1. Quicksilver - constantly used
2. NewsNetWire - basis of daily web surfing
3. Yojimbo - but being supplanted by Evernote more and more
4. Yep - terrific organizer for pdf's
1) Safari- NEED INTERNET (I'll go nuts without it!!!!)
2) iTunes- NEED MY MUSIC (How bland would the world be without a constant stream of the Rolling Stones!?)
3) Mail- Need to stay in contact (although I sometimes wish that people would leave me the hell alone!)
4) iChat- Need contact with my friends (but sometimes I want them to bug off)
4) (tie with iChat) Transmission- No comment!
As for QuickSilver...I don't see what the big deal is. I just use it because it's quicker than Spotlight as an app launcher. I use DockSend for Transmit (or even NcFTP) to FTP stuff, and the terminal (Zsh) for any complicated file operations.