well, it would be a lake in a hot country, tropical, and I'd stock it with neon tetras.. very small but very colourful fish :)
Brook and Golden trout, the color combos alone would be awesome in the water
Large and small mouth bass and walleye.
I have a 1 acre pond at my house. I stocked it with large mouth, perch, blue gill, silver cat, and grass carp. Funny thing after 5 years only blue gill left. Guess they eat the spawn of everything else. There are hundreds of large blue gill now. May start over.
Piranhas. ...then I would invite me exwife over to go swimming ! Lol