If you're looking for trophy pike (40+ inches): Kinzua or P.I.
If you just want to catch pike: Bull Dam. Tons of pike and plenty of good shore fishing spots. Fish are overpopulated and stunted, though. I've never caught a pike over 32 inches there (Biologists netted a 34 once), and anything over 28 is rare.
Lot of sad specimens like this: