I'm a big fan of Firefox, especially Firefox 3.0 which is in beta, but have been reading a lot of good things on Safari 3.1 which I use as well. However, there is such a huge variety to choose from I thought I would bounce this around, here is what I have used or seen:
Explorer
Shira (very cool)
Opera
Sunrise
Camino
Flock (great for social networking)
Konquerer
Explorer 7. Too many inconsistency with Firefox at school with web based programs. Don't knock it until you use 7. Add Google toolbar and you have a nice package.
I have actually had great luck with Firefox, especially when it comes to using multiple windows simultaneously. In NC we cannot upgrade to ie7 due to a conflict with our state database. This same conflict is with the google toolbar (it shuts the database down!). So...for that reason, I am a firefox junkie!