Honorable Mention:
FireFox. I don't see it as "Mandatory" but it IS one of the first things I get after a Re-Format.
Daemon Tools
RealVNC
Max 7
Any Fun Game at the Time.
F@H - Duh...
7Zip - I noticed a lot of people saying winrar and winzip. This does both formats, is open source, and is free. Winrar and Winzip are not.
Notepad2 - I like Textpad, I don't want to pay for Textpad, though.
Putty - SSH, SFTP... Been a long time since I've used an unsecure telnet.
Daemontools - Everyone needs CD imaging