I'll second DOpus4, although I only really go into it now and again, it's useful - especially with LhaDir.
ToolsDaemon - yes, and also MagicMenus so you don't have to go to the top of the screen. ;-)
MCP - for all those little things that you just can't live without (and that otherwise would have to be in some separate prog), and FBlit to help keep things Faaast. ;-) (again)
NewIconsV4 with DefIcons - for those who don't have KS3.1 but still like pretty interfaces.
There's still lots more.....
