I'd love to hear other tools that you guys are using for your daily workflow.
For crazy power users, I'm a huge fan of vim+tmux+zsh combo as described in http://www.drbunsen.org/text-triumvirate.html
You can run tmux in iTerm2.
GUI (Mac OS X): MacVim, ClipMenu, YummyFTP, Quicksilver, iTerm2, SourceTree, FileMerge, Chrome dev tools.
GUI (Linux): GVim, Glippy, FileZilla, Synapse, Gnome terminal, SmartGit/SmartSVN, Meld, Chrome dev tools.
I don't use any advanced features of iTerm, though, I just use it over Terminal.app because it supports 256 colors. We have not been updated to Lion or Mountain Lion at work so Terminal.app is still limited to 16 colors for me.