I swear by my 6-year-old Logitech MX518...there have been nicer looking and fancier mice out there, but none can beat it in my opinion, and it doesn't cost an arm and a leg either. Goes up to 1600dpi (which I almost never use) and DPI is switchable with two buttons on the top and bottom of the mousewheel and configured in the Logi mouse app (but you don't need the app to use the mouse)...really, what more do you need?
'Now, we gave you a promise and we are bound by that promise and damn you for asking for it! And damn me for agreeing to it! And damn all of us to Hell because that is exactly where we're going!'