Adblock Plus
     To stop ads. Duh

BBCodxtra
     So I don't have to keep writing the IMG tags when pasting images or setting up the URL tags so I can make words into links

Download Embedded
     To get the mms:// addresses of video feeds

Downthemall
     To mass download from sites. I mass download /with and /wg/ threads on 4chin SUCK all the time

Image Zoom
     Sometime I have to zoom in on pics and I don't want to download the pic to use some other program just to zoom in

Paste and Go 2
     To Paste and Go web addresses. Yes I'm that lazy :p

PDF Download
     I hate adobe reader opening in Firefox (or any other browser for that matter)

Tab Mix Plus
    Much better control over tabs.

User Agent Switcher
     To bypass certain sites and forums where if you use the Googlebot user agent info, they won't force you to sign up to view their threads/info