Probably the only thing that really makes me (or I guess I should say, =made= me) unique in the cubing world is the fact that I've made really nice custom cubes. This involves printing out designs on photo paper, using a small amount of superglue to temporarily affix them to the cube, and then using multiple layers of clear nail polish to seal the stickers securely. The end result is a cube with a very unique sheen and smooth feel that you probably won't ever get to experience unless you've handled one of my cubes in person.
I actually started using clear nail polish because I got a store-bought Rubik's Cube as a gift and was going to use it as my first real speedcube. The one I had before was atrocious (see here and here, the one in back), and would later manage to be in the top 3 for the "worst stickers on a cube" contest at cubesmith back in 2005. (I won a free set of tiles as my prize for being in the top 3) I didn't have any cubesmith stickers at the time, and didn't want to deal with ordering them (I was still in high school, spending money on the internet wasn't as commonplace, etc. etc.), so I went with the nail polish solution instead.
There -are- other means of creating custom cubes out there, but none of them are really as good. You can get them done professionally as part of a promotion, but that's basically only for businesses that are trying to make cool swag. There are also sticker sheets that you can print onto with a regular printer, that have adhesive material so that you can stick them onto your cube after printing. There are okay, but the quality of the prints tends to be nowhere -near- the quality that you can get with regular photo paper. I've also heard of people doing things like this.
Some words of advice on the off-chance that you actually happen to be interested in doing this:
-When you're designing, make extra sure to account for the fact that your stickers will be separated by a noticeable amount when they go on the cube.
-Cutting out the stickers well is actually a non-trivial task, especially if you're me and aren't too good with crafty stuff. Just try to be careful and consider making extras in case you screw up.
-Feel free to experiment with different types of photo paper, if you can. Not only for print quality, but also check to see how the nail polish will sit on the paper. Ideally you don't want the polish to just soak through the paper and ruin the colors.
-There WILL be some smudging of the ink, since you're essentially wetting your photo with the nail polish. You can minimize this by trying to be gentle with your application, but a little bit of blur is inevitable.
-You absolutely don't want superglue to seep out the edges, so be sure not to use too much. It's just a temporary affix anyways.
-On the other hand, don't only restrict yourself to the middle, as then you'll have edges that are flapping up and that's all sorts of bad. Press firmly!
-You will need to spend a lot of time nail polishing. A LOT of time. You can't really do all of the cube at once, so it's easiest to do it one face at a time, waiting for the polish to dry in between coats. Each sticker will need probably at least 3 coats at minimum, 4 is recommended. More is better.
-Nail polish brands don't really matter too much, so you can get cheap stuff without worrying too much. Well, more like there -is- probably a difference, but
-You want to put on a smooth coat of polish on each sticker, making sure to overlap and hit the black plastic too, but avoid getting nail polish between pieces. Again, emphasis on smooth coat--don't skimp or the coating will be rough and uneven.
-Have a card or piece of paper handy that you can swipe between cubies, at the end to make sure that you don't have any nail polish.
-From my experience I've actually found it works well to use a "base"-type nail polish for the first 2 or so layers, and then a "top coat" for additional coats.
-Make sure to check for bubbles. Bubbling is one of your worst enemies here.
-Wear a mask if you'd like, so you aren't breathing in fumes.
-Make sure no one will touch your cube as it's drying. It'll be baddd.
-For bad polish messups (stray drop somewhere totally off), you can try using a -wet- tissue to wipe it off.
-Depending on what shape your stickers were in and what kind of cube you have, you might need to recoat every once in a long while (this doesn't apply to cubesmith stickers).
Note: Cubes that use nail polish -instead- of stickers are not allowed in competition. However, there are no regulations against clear nail polish as a sealant.
The cube I used when I was in my prime. The stickers are all cubesmith stickers, aside from the white center sticker, which is a custom square printed on photo paper. All stickers are sealed with clear nail polish.
Kirby ability cubes. 2x2x2s are actually great for customization because they require a lot less work (24 stickers as opposed to 54).
My biggest custom cube endeavor was the making of 4 Tetris Attack cubes, 3 of which I sold to members of the tetrisattack.net community (unfortunately, the site has been defunct for a while). You can see one of these cubes in action here.
Some pictures of the assembly process.
In addition to a handful of Sanrio cubes, an Idiot's Cube, and a bunch of other nondescript Rubik's Cubes, I also have a plushie Rubik's Cube that a friend made for me. =)