What would it be? I thought it would be interesting if the queen could also move like a knight. That way, she could move the same way as any other piece on the board.
Your ideas?
“En passant” is a stupid rule, IMHO.
My father and I, when we used to play, played without informing each other when we had the other person in check. That made it quicker because sometimes a player wouldn’t notice when they’d moved into check, resulting in a quicker checkmate.
“Castle” - No reason for that obscure rule.
Obscure?
Flamethrowers.
I almost added to the OP: “Other than en passant of course. Nobody likes that rule.”
Castlenig is strategic. It moves your king into a safer area and does so more quickly than making space and moving the night ,rook and bishop out one at a time. You would likely destroy you pawn line in front to get the job done.
I have never seen the logic of en passant. Make it go away.
Instead of a king, one of the eight pawns will have a sticker hidden underneath its base that marks it as the king. The pawns will be randomized before each game such that neither player knows where their king is, forcing them to effectively assault the opponent’s entire pawn line while simultaneously protecting their own. To make things more interesting, it might be neat if players knew which of their opponent’s pawns was the king, forcing each player to figure out where his vital piece was based on his opponent’s multi-layered feints.
Also, I’d like to make grandmaster-level bug house mandatory for professional players.
Interesting variant, but two questions: What would you replace the king with (or leave it a piece that can move one square in any direction with no other significance)? and how would you handle check?
The position of the pieces on the back row should be random. Opening theory is main reason I don’t play anymore.
Another excellent variation is 3 check chess. The third check you give wins the game.
All Chess must be 3D, played in a cubic.
Or
Any dispute in Chess may be legally settled with a duel–Cavalry Sabres (Cutlasses, for those with a Naval bent) at Dawn!
The moves of the pieces haven’t changed since about 1500. Since the game is still popular world-wide, this suggests there’s no need to change again. 
Of course any such change affects not just opening theory, but also middlegame tactics and established ending knowledge. It could wreak havoc with careers of established players and render existing chess books and magazines redundant.
If you would like a variant for you and your friends to play, I recommend Madrasi chess.
Games are much ‘calmer’ using this, so weak players can tackle stronger ones. It’s also fun! (I teach chess professionally and have used this successfully.)
Under the rules of chess, you don’t have to say check. In fact, when I said it to a Grandmaster during an international tournament, he looked surprised and said afterwards “Don’t say check! I know it is!”
If you move into check, it’s an illegal move, not checkmate. You have to take the move back, play another one and continue.
Actually castling is vital for king safety (as gonzomax said).
In olden days, players sometimes used to both laboriously ‘castle by hand’ before getting on with the game.
Junior players like this variant. It involves four players, is usually noisy and pieces get dropped. :eek:
Professional players prefer 5 minute chess.
Fischerrandom has been tried. I’m sorry you feel opening theory is a pain. I think it’s part of chess, like knowing the basic checkmates and tactics.
3 check chess sounds rather ‘single-path’ to me. Why doesn’t White play for 1. e4 2. Bc4 3. Bxf7+ 4. Qf3+ winning?
I think you’ve missed RikWriter’s point. This thread is about *changing * the rules. Allowing moves into check, allowing quicker checkmates, is one possible way of changing the rules.
You get something similar in Janus chess, where you have an extra piece (the Janus) that can move like a bishop and a knight… it’s actually more powerful than the queen, since it can checkmate the king without assistance of any other piece. Also, this variant is played on a 10x8 instead of a 8x8 board, which means that there’s also two more pawns per side, and the relative position of king and queen is reversed in the initial formation.
Not a change, but a friend of mine and I played a variant of chess that we called mirrored chess. In mirrored chess, your goal is to get check mate or to lose as many pieces as possible. Whenever either player can take any piece, they have to. Hiding the queen is an essential strategy in this game.
Fffft. Eggs and omlettes. 
As an aside, how much do you think game change if en passant was eliminated?
Yeah, I know. I think it’s excellent.
Because I play e6.
For those of you interested in playing different variants of chess, I just chanced upon a program called ChessV, which supports more than fifty different ones… including eleven 10x8 board variants, such as the aforementioned Janus chess, and also several that include a piece that moves like a rook and a knight.