Classic: Base/Jungle/Fossil
Haymaker Haymaker Haymaker and Haymaker
Or at least ban Super Energy Removal / Energy Removal
EX: Deoxys and on
DX-on was an annoying metagame, with the Holon engine in nearly every deck and things like Flygon Ex or Eeveelutions.
EX: All sets
If restricted to EX sets (not DP), it could be fun to play old decks like Mewtric or Flariados I guess...
DP: Majestic Dawn and on
LuxChomp, Sablelock and Donphan... why not.
DP: All sets
LuxChomp, Gyarados, Sablelock, Kingdra / Donphan and Jumpluff... why not. ²
I'm interested, whatever the meta chosen.