Other

Wondrous Items

Dice of Auspicious Fortune (D381)

Especially if you have an expanded crit range (or RPGA Lucky Strike cards), many days you'll find a crit in your set of dice rolls. RRoT anyone?

Elven Chain (MME)

Really expensive, but non-conditional +AC. Better for masters of defense or anyone who's DM allows MagicMart , but good no matter what.

Fortune Stones (AV2,12,Rare)

This refers to the level 12 Stone of Earth or Stone of Light or stone of any other keyword you can tack onto a power. They're actually great. The only problem is that they're all rare. Rerolls as a slotless thing is great, and then the item set power says you get a silly bonus to the rerolls you use. But as a rare? You'd rather have the Dice. Known results trump rerolls.

Ruby Scabbard (AV,5)

Draw your blade as part of your attack action. Besides the obvious "what if I'm attacked in a social situation" save a minor, it also allows you to wander around with something else in your hands (Wolfen Weapon?) that you're using for a property or utility power.

Solitaire (Aquamarine) (AV,16)

Rending, in slotless magic item daily form. Most of the time, another attack was all you would do with a Violet Solitaire anyway.. this is just limited to a melee basic, and doesn't trigger AP goodness.

Solitaire (Cerulean) (AV,21)

At this level, the trigger will happen far more often. But if you're really affected by a lot of effects, you likely won't be attacking (stunned, unconscious from the ongoing 50 necrotic damage, etc)

Solitaire (Cinnabar) (AV,6)

Encounter Power to reroll a save... but won't happen predictably.

Solitaire (Citrine) (AV,11)

Spending a Healing Surge is a more predictable need then rerolling a save.

Solitaire (Violet) (AV)

The best solitaire. Get and Spend an extra Action Point right now. Win more.

Solitaire (Zaarani) (AV,10)

Action denial on a crit, as an slotless daily power.

Tattoos

Backlash Tattoo (AV2,9)

Another off-action attack in item form. This one kicks in when you're bloodied for the first time in an encounter... so try and make sure you're next to someone you want to hit when that happens, and hope that the bloodying attack didn't have a rider on it that keeps this from working.

Consumables

Bolt of Transit (AV2)

For when you need to get to artillery that's up on terrain. Pull out your crossbow (or Bow, if you're an Elf. Or sling if you're just weak) and teleport there. Better if you have Distant Vengeance , but handy for anyone with a good Dex score or Focused Fury as an at-will.

Oil of Etherealness (MME,20)

A turn of phasing, or two if required. A high level common consumable and it takes your minor (at a level where that makes it non-viable in combat), so this is really just "6750 to break the occasional out-of-combat bit where someone wasn't thinking straight".

Vial of Darkness (MME,5)

Smoke Grenades! The rules for obscurement are kinda tricky, the key here is that if you're at the edge, you can still see out and attack out without penalty. The real use is, of course, total concealment to start stealthing.

Boons

Boons are things you can do because of some training, gift, or other story element. Mechanically they are treated like items: the DMG suggests that they fade away after 5 levels; but Slotless Items. Many are quite nice simply because they are slotless.

But as a general rule, you can't count on getting any specific boon. Living Forgotten Realms explicitly prohibits them, except via specific modules. They tend to be in DM resources, not player resources, and so on.

But you can't talk to your DM unless you know they exist, so...

Divine Boons

Avandra's Boon of Escape (DMG2)

If you wind up not having oath, shift to get oath. Great against tactical DMs who try and break your thing.

Corellon's Boon of Arcane Might (DNG2)

The feature should say "level 1 at-will power", but it doesn't. So if your DM won't kill you, ask if you can take Aegis of Assault for some free abusive transit or Dominant Winds for at-will flight. The overall rating assumes your DM won't go for that, and you'll take Magic Weapon (and be Int based) instead.

Ioun's Revelation (DMG2)

Static bonus to all skill checks. Nice. It frees up your head slot, among other benefits.

Kord's Mighty Strength (DMG2)

You know what else gives a good item bonus to melee damage rolls? Iron Armbands of Power . And that's a property, not a daily power.

Melora's Storm Blessing (DMG2)

Like phasing, you frequently like flight on an encounter basis. This boon gives it to you on an encounter basis, along with another property. Would be nice to get.

Pelor's Sun Blessing (DMG2)

Attack Stat bonus damage? Really only achieves deep-sky-blue status after 16th level, and assumes that someone in your party is a Morninglord (you?). But given those assumptions, rocks. On. Toast.

Sehanine's Mark of the Dark Moon (DMG2)

For the Ninjas. Insubstantial while hidden, which can be quite frequently for you.

Grandmaster Training

These are boons that you have because you've been trained. You'll probably have an easier time talking your DM into ignoring the "fade in 5 levels" language.

Davros Elden's Blinding Strikes (DMG2,11)

Gauntlets of Blinding Strikes , the training version. Good for Martyrs, or anyone else who desperately wants a daily multi-attack power.

Davros Elden's Defensive Step (DMG2,7)

Boots of the Fencing Master , the training version. +1 AC while you spam Overwhelming Strike , and now you can wear another pair of boots.

Five Stars Five Strikes (D404,13)

A move action to get four attacks/eight d20 rolls. They add a small amount of damage per roll, but that's not the point here... the point is that with an extra four attacks you can reasonably hope to crit with setup. The question is, since it's not statted as a weapon power, what happens if you crit? I have no idea, ask your DM.

Insight of the Vault (D389,4)

Crits hurt more. Grandmaster training that you'll want to keep if possible, although it's not a huge long term boost. The downside is the linked flavor involves crazy gnomes.

Legendary Boons

These come from Dragon 389, in a very flavor-rich article about character arcs called Origin Stories . All the boons upgrade, which solves that "fading" issue, but you will find less items because one of the found-item slots in the treasure is being taken by the boon.

Because the assumption of the article is that the boon is a key element of your character, you probably won't be able to "pick one up once it's cheap", and so the slotless aspect matters a lot less. This means that the opportunity cost is a lot higher, and that hurts the overall ratings.

True Kiss of the Mistress (D389,3+)

+2 to saves, and a daily power to move when hit. Feh.

Kingslayer's Curse (D389,3+)

At least it's thematic. The "items" vary a lot more, and since it's thematic you may talk your DM into allowing access to lower level ones, but you're still not allowed to have more than one. Fearsome Reputation has a nice encounter power for oath maintaince, and Face Me, Cowards isn't clear, but looks like another oath-maintaince effect. God Hunter is a trap for it's level.

Demonbound (D389,3+)

A daily summoning that does poor damage, but does have an instinctive effect. But without the implement keyword, you'll never get the damage up high enough to matter. The real value will be as a scout (it can fly, and later phase), but a large scout sort of misses the point.

The Fading One (D389,3+)

Like Kingslayer , more a collection of boons than a single upgrading one. Ghostfoot is really good for mobility at that level (and for several later levels). Lighter than Wind is basically just "+1 to hit" for many. Spirit Body gives two turns of phasing every other encounter. Any of those would be great to keep for your whole career. Life Drain is a bit of a dud (IR that happens when you hit. So only on opportunity attacks. But it will HURT if you get it off), but then the final two are good to great. (Phasing on charges, with a daily "stop the pain" power, and then crits stun as the level 28 boon.

Psionic Talents

These appear in Dungeon 177, in the Adding Psionics article. As with anything in Dungeon, DM approval may be an issue. They are flavored like Grandmaster Trainings, so are slotless items. Your DM may decide that they go away in 5 levels, because a general assumption of the treasure economy is that items are only valuable for that time frame.

Mecurial Mind (Dun177,3,13,23)

Unslotted speed bonus (while not bloodied). The encounter power (free shift on hit with at-will) is strictly bonus. Allows you to wear better boots, and still have enough speed.

Muddling Mind (Dun177,15)

A good item bonus to stealth, encounter power to turn your at-will into Eyebite.

Sculpting Mind (Dun177,7,17,27)

Bonus to athletics, and then an encounter power that says you don't need to roll for jump checks. The encounter power strikes me as more valuable... especially once it applies to your high jump.

Warding Mind (Dun177,4,14,24)

The bonus to Acrobatics is nice, since in my experience most Acrobatics checks are in skill challenges, when you can generally assume you're not bloodied. The encounter power is especially nice if you've focused on your AC: an extra +2/4/6 may move you off the d20 roll for a turn.