I am a big enthusiast of chess variants, and here are my favorites: English Progressive Chess Magnetic Chess Knight-Relay Chess Grand Chess Avalanche Chess Glinski Hexagonal Chess Fortress Chess
I've also developed an affinity for Ice Chess since it was added.
(hide) If you want to play a game with an opponent of a similar level, you can define a required BKR range for a new game invitation. Then nobody with a BKR outside this range will be able to see/accept it. (Katechka) (show all tips)