Applications I couldn't live without:
Web browser: Mozilla FirefoxFile sharing: eMule AnalyZZUL
Instant Messaging: Miranda IM
IRC client: Gamers.IRC
(well, I'm in the team, so I actually should use it, too)Audio player: Winamp
Image viewer: IrfanView
All the other stuff I use, including my mail client and my chosen text editors, are not an actual "must-have" for me, I could easily go with alternatives...

Well, just for completion, these are my
beloved other ones:
Text editors: Notepad++,
Vim
E-Mail: Mozilla Thunderbird (unless I manage to know The Bat! better)Video player: Media Player Classic Home Cinema
Writing documents and stuff: OpenOffice.orgControlling Windows: ac'tivAid
Task manager: Process Explorer
Version control: TortoiseSVN, CommitMonitor
Not much
platform-independent stuff, I know... but this is not a criterion for me.

I use a real bunch of
other applications not fitting into any of the categories above. I just think "must-have" is not "I always had it and it is quite useless for my typical PC usage but I love it".
