I have been fascinated lately with variations on chess. The one played by many in Europe, including current Grandmasters, is Janus Chess. The board has two extra spaces (10 x 8 board) and each side has a Janus, a combination of a knight and bishop.
Having a combination piece means that a player can be checkmated with a Janus alone.
Reading about it, though, I stumbled upon a website with many, many different chess variants. People have combined pieces of all kinds, including ones from Shogi (chinese chess) and Tamerlane. Folks come up with some wild variations, including some rather unplayable ones. There's a rabbit that can make as many knight moves in a counterclockwise fashion as it can. (Am I in check from your rabbit? Let me check.) There's variations of the knight that make the "L" longer, wider, or both. There's a checker piece that captures by jumping. The list is really large at chessvariants.org.
My favorite, however, is Chess with Different Armies. Four different armies have been playtested by the inventor and it is fascinating to see a game being played. Both sides are pretty much equal, but the tactics of each of definitely not the same. I imagine a tournament where players can switch armies between matches. I imagine two variant armies squaring off will be the most exciting matches.
If I ever live out my fantasy of opening a store, I'd like to create and sell Chess with Multiple Armies. It could be like the release of Deadwood with new armies every year. Heck, I may do that anyway.
Of course, I also like Arimaa, designed to confound computers. Enjoy the wikipedia reading.