My own first experience with "alternative" rules was soon after I learned chess, at the age of 6 or 7. A schoolfriend who taught me claimed that pawns couldn't capture on their first move. This lead to various attempts at smothered mate, usually involving the plan Nb1-c3-e4-d6# This all went well until I tried it on my father, who both took my knight, and taught me the correct rules of chess.
Since then I've come across a number of "rules". Here a a few that I can remember (all of which are untrue btw)
Promotion (All ways a rich vein!)
- You can only promote to a piece that has already been captured
- When you promote to a queen you have to put it back on its starting square
- If you promote the a pawn you must take a rook, b pawn = knight etc (What happens with the e pawn? Two kings?)
- You have to leave your pawn on the back rank for a move before promoting it
- Can't castle if your rook is attacked
- King goes to h1, rook to e1
- Pawns can capture pieces en-pas
- En-pas works any time a pawn passes another
and finally my favourite (courtesy of a recent Geurt Gijssen Chess Cafe Column)
- If you only have a king left, but you manage to get it to the other end of the board, you add an extra rook to your side.