Another vote for Logitech, any of the MX series, just depends on what you like. Personally, I went with the MX700 because I use it for presentations and such, but am also a gamer and I have no complaints with it, it has a nice smooth movement and doesn't skip no matter how fast you move it.
On a side note, I have had 3 MS Intellimouse Explorers and each has broken within a few months and I have yet to break a Logitech mouse.
