This is going to sound a bit weird, but if I am in the middle of a moment of deep despair then eating something with hot peppers snaps me out of it. Something like Tabasco on popcorn, or Buffalo wings. Or sometimes just munching on sandwich peppers.

It doesn't really "make me happy", but it can remove that deep depressive feeling. Or if I'm in a good mood, it can kick-start an intensive programming session.