Index and middle, when I was young I used to be able to incorporate the ring finger. During the mid 80's a few of us ended up in a fight with some local skinheads
and I received a kick which somehow went between my middle and ring finger, luckily neither finger got broken, but damage was done
and as a result my ring finger now rests at a slightly off angle towards my pinky.
On the up side though, I found I can do a Mr Spock "Live long and prosper" gesture as easy as giving someone the V's.