Mozilla....
1. Plugins. I don't know how many plugins I have but it's definately a large number.
2. Tabbed Browsing. I know that a lot of other programs do this but Mozilla does it best with Tab Groups and bookmarking groups of tabs.
3. Sidebar. Customizable sidebar with Bookmarks, Search, What is Related, History, RSS Feeds, and more.
4. Plugin finder. One of the most over looked features. Mozilla features a plugin finder, giving you the exact location of a plugin needed to view certain components of a website.
5. E-mail program integration. Mozilla features its own POP3 client with integration into Mozilla. If you like a different client or one that uses a different format, you can get a plugin to intercept clicks and use an associated program to open them.
6. HTML editor. You like the layout of a website? Stealing just got easier with the Composer in Mozilla. I stole the layout of Microsoft's webpage and am currently redoing it for my own personal gains.
Muhahahahahaha!
7. Address Book. Found something you want to share with your friend? Look up his number and e-mail address with Mozilla's Address Book.
8. Chatzilla
By far one of the best features of Mozilla. I use it to get all of my Messenger Plus! news and support. Not to mention to get my
addiction.
9. Download manager. While IE only lets you have 4 or 5 downloads at once. Mozilla lets you use all of your bandwidth to download files.
10. Password manager. Mozilla will remeber and autofill your passwords according to website. If you have more than one password, it will ask you. And don't worry about privacy, it's encrypted by a 128 bit AES encryption system.
By far Mozilla is the best browser. I tried Firefox, but it didn't have the support for Mozilla plugins that I liked. I absolutely DISPISE IE for its security holes.