Ctrl-C seems to work in any vim (though, I think, not actual vi), and at some point my muscle memory rewired itself to that. It's usually directly under my left hand, and it's a keyboard shortcut I use elsewhere, like in the shell.
ctrl+[ works in any vim because it sends the exact same character as Escape. Unless your terminal emulator is very oddly configured, then it will work the same.
Having caps as ctrl makes it really easy to hit.