I think Arnold may have the most appearances in a pin (T2, T3, LAH), next to Gary Oldman (BSD, BDK, LIS).
What are the chances that both of these guys tend to show up in the best games?
My runner-up has to go to Tim Curry. The dude shows up in two of my favorite pins, The Shadow & Congo.
BTW....we need to add Ian McKellen to the list. The dude shows up in The Shadow and Stern's LOTR.