I like the really technical courses where the guys at the front can set a pace that shells people every lap.
Short courses are a plus too. Better for the fans, better for lapping attacks.
Downtown crits are awesome with the shadows of the tall buildings and the crowds that come out.
I also like racing weekly at our local auto track because the asphalt is a different mixture with more sand, so you have much more traction than out on roads, and the rain traction is 100x better than the roads.