The safest browser is probably Lynx. It protects you from scripts, flash, and everything else (except text). /sarcasm
It probably doesn't matter which one you use; I'm sure they all have exploits. As long as you're smart about what websites you go to, that's probably the best protection. I like to use click-to-flash, so you have to approve flash before it runs on a page, and I'm sure you can find similar plug-ins for other browsers. Beyond that, you could disable javascript and a ton of other things, but that makes it hard to use a lot of websites, so it's best reserved for tinfoil hat-wearing security experts.
Quick guide if you're really interested:
http://www.cert.org/tech_tips/securing_browser/