As a Mac user I use the app Quicksilver, brilliant for launching applications without having to click around with a mouse. Secondly, the caps lock key is an annoyance that has to be dealt with. There is no option in Quicksilver to use caps lock as a shortcut key (as it was with Enzo for Windows), so the quickest fix that gets you 90% of the way is to reassign the caps lock key to the option (alt) key in System Preferences > Keyboard & Mouse > Modifier Keys > Set Caps Lock to Option:
Then in Quicksilver, make whatever shortcut you want the “regular” way of launching it, and at the same time set Modifier-only Activation > Double > Option
You don’t want to launch Quicksilver each time the option key is pressed, therefor the setting is Double instead of Single. Whenever you now double tap the caps lock or the actual option key, Quicksilver will come up.