Another common one is Capslock.

Mapping capslock to be esc is what made vim possible for me.

Agreed. I don't know how anybody could use vi with escape unmapped. It's also very useful outside vi though, since esc is the default 'cancel' key in many cases. For example, most browser dialogs (and keyboard-navigable menus) can be closed with esc, and it works for many desktop dialogs too (at least on Linux).

Im too lazy to move two fingers for that, instead mine is mapped to jj. =P

What is jk?

Just key 'j' followed by 'k'. I have this in my vimrc for quickly jumping out of insert mode: inoremap jk <ESC>

To each his own. I'm very fluid with my esc key hitting. I find it to be a very satisfying motion.

imap jk <Esc> In insert mode. First press j, in the same second press k.