Most probably take Crimson Stride for the "fetch" element. Or they look back at the other off-action attack they passed at 3rd level, and pick that up.
Avenger's Demand (DP)
The pull is an effect, so when you make your attack you'll still get your rerolls, and then it pushes and knocks prone as a kicker. Remember, prone and Adjacent is roughly equivalent to immobilized, especially if you have a decent OA.
Cloud of Souls (PHB2)
Keeps enemies away from your target, but not away from you. Useful for blocking a choke point, but that's about it. Better for the Martyr, as it turns into a beautiful (half secondary stat) setup power. Shame you don't yet have anything great to follow it with.
Crimson Stride (DP)
Sequestering Strike's older brother, now with approach as well. Comes with a special for every censure except pursuit. Weird. Still good for everyone.
Dervish Strike (DP)
The visual is cool, and mechanically you get some extra control, and you give the target a free head start in case it wants to run (or you want to spend an action point to charge it)
Light of the Avenging Sun (PHB2)
Radiant damage, and your target is unlikely to hit you for a turn. That might convince it to run...
Weaving Blades (DP)
Even more accurate than normal, and one turn of "push everyone who would deny you your oath".
Whirling Blades (PHB2)
A nice boring 3W if your target is feeling lonely. For a class that started with 2W encounter powers and ends up with 6W ones, it's a shame that 3W is considered a pure damage power at this level. Dervish strike also does 3W, and does more than just damage.
Lifedrinking Covenant (D382)
Range, but with rerolls. Strong encouragement for your target to stay. And damage for each square the target moves is nearly immobilize. If you're either a Radiant One , or if you're in a push-happy party with a bloodmage , could be spectacular.
Sequestering Word (PHB2)
You and your target go 5 away to talk, and then anyone who doesn't move away from you takes damage... but it's your ranged implement power. Otherwise it would be an automatic choice for Chasers. Instead take Crimson Stride.
Wages of Sin (DP)
Ranged Implement attack that does "extra" damage still less than what you'd do if you just ran up and hit it.
The Barbarian Rage Strike power indicates that 6W would be a good pure-damage power at this level. Oath of the Many comes the closest at 4{W}.
Aspect of Fury (PHB2)
Start with a possible 3W attack, and then start a 5 point damage aura that also hits anyone who attacks you, even with reach. Chasers want. Anyone who wants a lot of DPR wants.
Bond of the Sacred Duel (PHB2)
The initial attack is weak, but the rider isn't too bad. Think of it as nearly doubling your retribution bonus. The downside is that it might mean you stop getting a retribution bonus, but that's not a horrible fate.
Forceful Call (DP)
Daily Come and Get It (but only does damage to one target, not all hit). What's a great power for a fighter is a horrible horrible avenger power.
Ghostly Chains (DP)
You use slow/immobilize on melee threats, so you get more rounds to pick at them in perfect safety from range. This asks you to have allies adjacent to the target. Wha?
Inescapable Justice (DP)
Free movement back to your target until it dies. Eh. Again, most monsters don't actually run without substantial incentive.
Oath of Divine Lightning (PHB2)
The chaser who penalizes saves can do decent things with this... but there are better control options at this level. Chasers should look at Aspect of Fury instead.
Oath of the Many (D382)
The biggest {W} since Living Death Strike, and until Oath of the Inevitable Blade... and it has an effect: two oathed enemies. Another way to avoid taking Refocus Enmity, but since you have to kill both of them to regain your oath power, not quite as good.
Tether of Light (DP)
Sequestering strike for every hit for an encounter. Please have an intelligence modifier.
Zealous Onslaught (DP)
Just an attack with a "Grants CA (save ends)". The kicker is a free MBA, so this is a multi-attack for Elites/Solos that don't stun.
Sigil of Carceri (PHB2)
Ranged. Seriously annoys one artillery piece (save-ends)
Soul Lightning (DP)
Ranged. Target hurts close allies to the tune of 10 lightning per round. As a daily, that seems underwhelming simply because of the HP monsters have at this level. As a "Leave me alone" power, pretty radically inferior to Temple of Brilliance
Temple of Brilliance (DP)
Another "guarantee you your oath" power. No one on team monster is getting within two squares of your target, because it is guaranteed to be blinded. But does basically no damage, and doesn't otherwise affect the target at all.
Astral Cloak (PHB2)
A turn of invisibility. More things for the Ninja.
Battle Blessing (DP)
Because it's an interrupt, you can use it after you know what your ally rolled. Which translates to "Trigger: Ally crits on an opportunity attack". But that's still really conditional.
Bulwark of Defiance (PHB2)
Your wrath pushes you to ignore a save-end effect for a turn. Not bad as an encounter power. It will combine well with Superior Will for some things that are not save-ends, which is an added boon in LFR or other campaigns where the adventure author recognizes the inversion between the severity of "save-ends" vs. "End of Next Turn".
Pillar of Chernoggar (DP)
Stance that slows everyone next to you. That's some control. Pair with a storm sorcerer for maximum fun, even if you stop getting your oath.
Refire the Forge (D385)
When you get bloodied (or dropped) by an attack, make a free attack as an interrupt. And, oh yeah, all your attacks heal you for free. Your DM will quickly learn to drop you with Aura damage or other non-attacks, but if you can hover around bloodied you'll probably get a fair number of triggers. Your DM may decide that the trigger is "applying the damage" not "getting hit", and thus killing the monster doesn't negate taking the damage. But you'll still heal, which will usually take a lot of the sting out. If you're already dead or a minotaur it's even better, because you'll get more chances to heal from sub-zero (and thus never get around to actually falling over)
Strength in Unity (DP)
Once an encounter, ignore one attack. At least if you have an intelligence modifier and stay near your party.
Summons to Duty (DP)
Slide an ally into a flanking position as a minor. Good for the leader minors, but a little high level for the effect.
Temple of Seclusion (DP)
One encounter a day, get your oath every round without having to worry about it. That's great ... but at this level, I find you're fighting more large creatures, and less monster-created lines. More elites, less minions. You're typically less likely to have oath problems, so in less need of a fix for it.
Vengeful Revenant (PHB2)
Especially for the Deva. Pop back up like the energizer-bunny powered terminator you are. But for it to be useful, you had to fail a death save, which means your leader let you have one. It's good in that it's stable, but it should be useful only in a really really rare situation.
Winds of the Astral Sea (PHB2)
For a 16th level encounter power, that's an awfully short teleport.
Most should take Vengeful Parry or Soulforge Hammering . Off-action attacks or multi-attacks are how you win in this edition as a striker. If you're low on Phasing, look at Wrathful Charge.
Accept no Defeat (DP)
Basically, it's a 3W pure damage power with a really weird miss clause. Take something more interesting.
Haunting Step (D382)
It's an good range power that (for Unity) can teleport you instead. A 3{W} approach power isn't bad, but this level has better.
Lethal Intercession (DP)
I don't know how often you draw OAs, but I'd guess that only Polearm Gamble avengers take enough to consider this power. (The language isn't well defined, but your DM knows what they mean). At which point, it gives a small attack debuff. Er, woo? Better for PMC stunts that get a defender aura, or Tactical Warpriest s, because then you're using the -2 to try and force a miss. But then the poor wording comes into play.
Punishing Blow (DP)
I honestly have no idea what this is supposed to do. Each enemy adjacent to the target counts as your Oath Target? So I guess that means you can hit them with Painful Oath bonus damage, but you still only get rerolls based on being next to only one creature, so you won't get oath rolls here.
Ready the Final Blow (PHB2)
A setup power for the Chasers. You stick your victim in place, and get a "Dear God" bonus to hit him with your next attack roll. Or if you have a leader, you could use Soulforge Hammering to kill him this round, and do something else next.
Soulforge Hammering (D385)
An explicit multiattack, designed to favor "real" avengers over crit-fishers. 3 attacks over two rounds, using your minor action, and all your attacks gain an off stat to damage. This is your Nova spike of choice.
Spectral Charge (PHB2)
Charge, and take half damage from any attacks you soak up on the way in, and for the next turn. Wrathful Charge is more offensive, this is more defensive.
Vengeful Parry (DP)
Immediate Interrupt, with a trigger almost guaranteed to happen. Sold. Oh, also... it moves the target and can keep you from being hit at all. (Take the shift after your counterattack but choose not to slide the target)
Warding Blade (PHB2)
First you clear the space around your target, and then you punish any enemies that come back (or if you have reach, attack you from outside). And if you're Martyr, you Will hit with those opportunity attacks.
Wrathful Charge (DP)
Charge through walls and enemies, collecting damage bonuses for each enemy that attempts to attack you. And if you're retributive, you get silly bonuses even if your missed. (Um, once for each time you're missed on the way in, and twice for each time you're hit. Wow, that could do a lot of damage). Unfortunately, the power's damage bonus only applies to the power... but your censure bonus will stick around for another round. Safety Tip: Incompatible with Badge of the Berserker. Lesser will still work, partially.
Astral Fury (PHB2)
Melee Touch. One or Two (??) targets get teleported and immobolized. Vs. melee brutes, this is basically an encounter stun. vs. Artillery, it's useless.
Chains of Letherna (D380)
Ranged. Low damage+Immobilize, and a "don't get near the target" effect that's so little damage only minions will notice. Bah.
The Barbarian Rage Strike power indicates that 7W would be a good pure-damage power at this level. The best here is 5. Controllers get their upgrade to Glaring Admonition, but for everyone else this is not a great level... Blade of the Astral Hosts could work well as a big round for a Martyr...
Blade of Astral Hosts (DP)
Try and make sure your oath target is in the first burst, so that it works as a multi-attack power. But it's a daily pure damage power, which I'm not a big fan of. It's still probably the highest damage power you have without multiclassing or using cheesy readings.
Bonded by Blood (DP)
This level's "Chase after your target until it dies" power.
Flame Unquenchable (DP)
Good: 3W and applies a penalty to your targets saves against ongoing damage. Bad: The penalty is ridiculously conditional.
Leprous Wound (D380)
This is a power that is optimizable to something silly via a cheesy reading, and BB tricks. But since you're almost level 21, Radiant One is right there. If you're not a Radiant One and also think that the obvious reading is that the 10 extra damage are considered to be part of the triggering attack: meh. You'll still hit the target with around 50-90 extra damage, depending on your party. That's still pretty good.
Oath of the Inevitable Blade (PHB2)
Finally, a 5W. The miss effect is weak, but you used it after one of your setup powers, right? So how can you miss? (Shoulda been 7W and Reliable)
Stroke of Doom (DP)
Its a weapon vs. NAD attack to pull the target, so it's fairly accurate even at range. But the followup is just a 5{W} attack. Yawn.
Temple of Respite (PHB2)
A nice defender/controller power. Your defenses to up, you are surrounded by difficult terrain. But not that much damage, and you're not usually a defender. Also, needs more dakka. Remember it doesn't move with you, so make sure you use it at a choke-point.
Vengeful Recovery (PHB2)
If you hit, the kicker is free healing. If you miss you still heal, you just have to spend a surge. And it dazes too, always. But since you're not an Orbizard, save-ends conditions other than stunned are overrated. Also, needs more dakka.
Aspect of Awe (PHB2)
Close Burst, one target. Lame damage and a save-ends pull effect. Um, why?
Radiant Beckoning (D382)
The upgrade for Glaring Admonition. Still a power-tax (which is more expensive than a feat tax). The effect on your target is completely useless, (5d8+pull 5). But it's got the "use ranged attacks like you're supposed to" effect that should have been a feat.