IE and opera are the only ones worth a damn on that list. I use firefox for the most part though I've also got IE8 Opera and safari installed. II like safari aside from the fact that it doesn't let you middle click/scroll. that was a deal breaker for me. FYI netscape is worthless it's no longer even supported or developed. AOL basically told users to go for firefox.
Firefox. It has many addons and plugins and doesn't have a huge UI like IE does. (It gets a bit annoying to me) Firefox also supports .png transparency.
WELLLLL.... I accidently NULLED my damn vote but I use Opera. Always have and most likely always will. When I am doing some design work or something I use Mozilla (NOT FIREFOX) but I don't normally do that.