Have I mentioned I love Mass Effect? And how much? THIS MUCH!!! (Note that it's an ADULT colouring book. Totally valid excuse to buy one.)
The illustrations are pretty cool too. Check out Wrex here, for example. And you get a fun quote for every image.
But Garrus is my favourite, so I had to start with him. The thing is, it's really hard to remember which bit of the armour is which colour. Luckily, I came up with a solution.
Work it, baby! Blue Steel!
Totally worth the money.
(I got mine on Amazon, but it looks like these are pretty widely available. Oh, and Dragon Age has one too! Looks like they're going for about ten bucks right now.)