Advanced user-definable keyboard shortcuts. The current Keyboard Shortcuts feature (in the Keyboard & Mouse preference pane) is a good start, but still too primitive. I can break down what I'd like into a few parts:
° App-by-app and system-wide shortcuts for AppleScripts and Automator workflows. The current Scripts menu is great, but it's incompatible with the Keyboard Shortcuts feature. Which brings me to point #2.
° Support for menu extras. If it's in the menu bar, and brings up a menu when you click on it, then it's a menu! I'm not sure what all would need to be done for this to work; possibly menu extras would need to be rewritten. Whatever it takes, do it.
° Non-menu-based shortcuts. This would require apps to be specifically written to support it, but it would not be hard to do. AppleScript was a step in the right direction, but is still a liiittle too hard to use, for both users and programmers. Same with Automator. With Cocoa, you already have a very, very easy way of sending actions by name. I want to be able to arbitrarily execute any Cocoa selector (sorry if I'm getting too geeky here) from a shortcut. Of course, developers would need some way to specific mark which selectors would be available for this kind of interface. It wouldn't take any more than a few lines in a plist, though.
° Macros. Automator's a great step, and AppleScript's great, but Automator is still very limited and AppleScript is a terrible hassle, especially for average joes. Give me a simple way to simulate keystrokes and mouse clicks, with recording abilities.
While we're on the topic of keyboard shortcuts, let me change this from "what I'd like to see in Leopard" to "what I'd like to see in the future of the Mac": MORE FKEYS! PLEEEEEASE. Back in the old days, fkeys were supposed to reserves strictly for the end-user's customization. Then third-party apps started hijacking them. Then APPLE starting hijacking them, with everything from Exposé to brightness control to bloody VoiceOver (okay, that's not a raw fkey, but still). Bottom line: the software has evolved beyond the 15 fkeys. WAY beyond. Give me a whole other row, and make it cleat than at least some of those are strictly for the user to program (most likely using the advanced keyboard shortcuts I'm asking for).