Internet Explorer, of course!
Kidding.
Safari, but only because I'm using OS X. If you're using a PC, you should most definitely use Firefox, but for me, Safari is the only way.
I have no need for a ton of plugins. Using Safari, I have two plugins installed; Safari AdBlock, and ad blocker, and Inquisitor, and spotlight-like add-on for Google searching form the toolbar. Other than that, Safari includes everything I need in a browser. It's simple, has a nice, clean UI, and is very easy to use.