OSX Tools I use

Misc:
ClamXav - antivirus
Evernote - for note taking
Handbrake - for media conversion
LibreOffice - for working on office docs... though starting to use Keynote for presentations
Onyx - mac maintenance app
VLC - for watching media on the mac
Transmission - for bittorrent

Internet:
Adium - for XMPP and stuff
Colloquy - for IRC
CyberDuck - for FTPness
Firefox - for browsing
Opera - for fast browsing
Skype
- Call Recorder - for recording Skype calls

Dev:
Mono - because I'm a C# hack
RubyMine - to help me feel less bad at Ruby
TextMate - Editing things
VMWare Fusion to virtualize things