It's no secret I'm a huge fanboy. I love stuff that fits with my faction of choice in games, be it buttons, dice, shirts or pins. Unfortunately it's not easy to come by this stuff for every faction or game system.
I've used Chessex Custom Dice for several projects and have always been happy with the results. The process is fairly inexpensive and really easy. All you have to do is send them a jpg or eps file of the logo or design you want and they can engrave it on the dice. The catch is the logo has to be one color, as it's not a photographic process.
Also it seems like logos that are more solid show up better than things that are outlined. Important to keep in mind as a few of my friends have ordered dice that just have thin outlines and they're pretty hard to read.
There is a limited selection of colors but for the most part you can find something to fit your needs. I've used them to create six-sided dice for my 40K army and have found they seem to roll better. Of course when using rending lightening claws it's always great to see a bunch of ravens show up.
I recently found out that they can also customize ten-sided dice. Having recently got into MERCS I have been looking for dice to match the color scheme of my chosen factions. After doing some research I found that ordering a set of ten customized dice isn't really that much more that buying a good set in an odd color.
Overall I'm really happy with how they turned out. And having something cool and different that no one else has is well worth the $15 a set they cost. I highly recommend the custom dice service as they have the best quality and price of any manufacturer that I've looked at.