Gimmick metagames imo
like "your deck cannot have any Primes" or "your deck must have only Y type pokemon" or shit like that. I'm bored of SP vs Gyara vs Machamp, tbh.
Alternatively, roulette battles, where everyone adds a .dek file to a pool, and we all pick a random one, meaning everyone should get a deck they've not used before (unless everyone throws in SP which is just suck).