I have sort of a tie between Firefox and Chrome. I use the former a little more than the latter (maybe because of the add-ons?), but if I don't want to one because my computer may go slow I'll use the other. I have Safari as like a backup, even though I rarely use it, even updating it.
I don't think I would want to use Internet Explorer, no matter how many times it's been updated.
Sometimes I use built-in browsers in software like Winamp, but that's not very often.
For my Android, I use Dolphin Browser HD because it's more flexible with the web content than the unnamed stock browser. I even have it installed in my mother's if I'm close to using my bandwidth limit on my phone.