George Lynch uses his Middle finger. Besides I started using just my middle finger to tap when I got heavily into sweep picking. As a result of me doing sweeped taps I started using just my middle finger because that's what I became used to and found it easier.
I remember a long time ago when I first started playing Van Halen tunes (Forget how to play most of them now) I used my main finger. Now I use just my middle one. :-)


Another note...sorry for getting off of the subject.