I use an old microsoft intellimouse optical i bought for $80 more than 10 years ago. Still the nicest scroll wheel I've found, and I've grown too accustomed to the size and shape to contemplate a different mouse. Pity about the awkward positions of buttons 4 and 5.
Keyboard was nicked from a Dell GX520, it's got media buttons and a volume knob, plus some internet buttons I don't use.
Mouse mat could end up a family heirloom, has to be at least 20 years old now. Probably what I should replace first, although I doubt changing any of my equipment would improve my gaming in the slightest.