I would have to say a 15-acre farm pond my family owns in Ohio (where I grew up). Everytime I go back to visit, you can find me and my younger brother out on the 12 footer. Tons of bass, crappie, and bluegill. Just to give you an idea, when I was up there in May, we fished there for 6 hours on a Saturday morning and hauled in 142 fish between the two of us (and no matter what my brother says, I caught more than he did...). You're almost guaranteed a fish (or at least a strike) every third cast.
The only bad part? It spoils the expectations for everywhere else you go.
Indian Lake, Alum Creek Lake, and Lake Erie all come in a close 2nd. I love me some Fried Lake Erie Perch! Just getting used to fishing down here in Florida. Lots of good water down here as well.