I just don't remember what DOS game it was that had actions linked to all of CTRL, ALT and DEL.
It were some actions that one wouldn't usually use together. I, as a bad gamer just didn't at all, but some people were able to put more commands per second there...
I worked at a gaming event a while back, where the players were using hardware we had bought them to match what they had at home. One of them changed the crouch binding from Ctrl to alt (to use the thumb) and the default bindings for the keys on his moise were f1 through f4... He alt+f4'ed out of his competitive game in the middle of the round, twice, before we actually figured out what was wrong.
It were some actions that one wouldn't usually use together. I, as a bad gamer just didn't at all, but some people were able to put more commands per second there...