Graham Chex: The original one they had in the 90's with actual graham crackers in it.
Fruity Pebbles: My only regret is that they don't put more in the box.

Frosted Flakes: One of the classics, and a great value for the buck.
Corn Flakes: Even moreso than frosted flakes, and has other practical uses as well.
Cocoa Pebbles: Same as fruity pebbles. But for when I have a chocolate craving.