I primarily use Opera. In the rare instances that Opera doesn't work as I need, I'll use Firefox to do it. When playing a flash game like Evony, I find Chrome does best.

I only use IE when there's no other browser to use, which generally only happens on new/refreshly rebooted computers. This is of course a very temporary situation.

I haven't used any other web browsers yet. I've considered trying out Safari just for the experience, though.