Chrome now, at home on Mac and at work on Windows and Linux.
Used to use Internet Exploder, before I learned better. Atrocious performance, non-standards-compliant. Too many toolbars. Only recently got tabs. Takes down the OS when it crashes.
Used to use Opera, before I learned better. It was great until they fscked up the tab order, last time I tried it seems to randomly switch between tabs when you close a tab.
Used to use Safari, but only to test stuff at work. It did some weird things, like closing all tabs when I pressed the back button, and had different font rendering to all other browsers.
Used to use Firefox, but performance sucks, memory management sucks, UI kinda sucks recently since they removed the menu and added a huge empty wasted space at the top where it used to be.
Chrome works. Cross-platform. Good memory/process management. Consistent handling of tabs. Good performance. Good developer tools. Nuff said.