I love the GoldenIMAGE 3-button optical mouse that I got with my A3k, second-hand. It's got an Amiga/Atari switch on the bottom, so it's not build specifically only for Amiga.
It uses a special mouse pad, but it's not one of those horrible rigid reflector ones (like what I used in Uni on Sun boxes). It's flexible, grey, with a pattern of dots on it.
I've found that it also works (imperfectly) on denim.
