I started using
the G-13 about three months ago to play World of Warcraft, and it's amazing. I don't need to use the keyboard to navigate anymore, as it has a little joystick for the thumb. I can set all 25 keys to whatever configuration I want, which means I rarely have to move my left hand during play.
I haven't played a FPS in years, but I imagine it would be quite handy for that, too. If you have multiple games, it can be programmed with four different profiles that are easy to switch between.
I use a basic 5 button optical mouse from Microsoft that I've loved for 10 years. It's not the most durable mouse in the world (I tend to go through them pretty fast), but it's very comfortable, and I'm used to it.
For the PS3, I think they finally got the controller just right. I wasn't a fan of the PS2 controller (I didn't like having double shoulder buttons), but the new one is much better. I don't use third party controllers anymore.
What sort of peripherals do the rest of you like?