Opera has better tools, is faster, and generally all around better. As a developer, there is one things it is missing that I always need, which causes me to use Firefox - the view selection source right click tool. That is a must have.
Chrome is pretty cool, I like their incognito feature, that 'comes in hand', lol.
After all of the problems I've had with Internet Explorer, I'd have to say Firefox 3. Although, I do really like Opera, seeing as it's fast, easy to use, and has several tools.
Google Chrome is also O.K., but I prefer Firefox.
Firefox is my favorite. After reading the comments ^ I might have to actually look into Opera. But I'm a Firefox girl. It's not perfect, but I love the addons for it and such. I can't stand IE anymore.
Internet Explorer, by far, is the worst pick for a web browser if you are concerned for safe browsing. There have been issues, even in the past 5 months where Internet Explorer was having issues with security. It is perhaps the most popular of web browsers, since many people do not even know there are browsers other than Internet Explorer, since it is Microsoft's default browser. This is my least favorite browser.
Opera is without a doubt, the fastest of the listed browsers. Opera is increasing in popularity, due to the rather useful tools equipped with the web browser. It is much superior compared to Internet Explorer.
FireFox is the browser I am currently using. FireFox is the browser that is probably the second most popular of the web browsers listed. There also have been issues with FireFox with security, and like Internet Explorer, can have frequent issues with crashing. It is much faster than Internet Explorer, and much safer.
If not FireFox, I use Safari. Safari on a Mac has incredible safety, and isn't plagued with often bugs and security issues like Internet Explorer on Windows. I am yet to find any real flaw within Safari, since it is rather stable for a web browser. It is often even disputed that FireFox is slower than Safari.