I wonder what shortcut TextMate has that *isn't* system wide that people miss the most. For me, it's definitely ⌃W to select the current word.
Control-Arrows to jump through partial words. Hands down.
Actually, I take that back...Command-E is common for using selection as "find", and Command-G for finding next, but Command-Shift-E to use selection as replacement and Command-Option-F to replace and find is probably even more wished-for outside of textmate than Control-Arrows. For me, at least.
+dru