We do a christmas themed one. No legends, 6 vs. 6. And a twist every round to your team.
My way.
You can build your team, no legends, ubers, chatots, or wobbuffets. 6 on 6. A twist every round.
ex: This round, you must have one green and one red pokemon of your team
ex: This round, fire types are banned!
And so on.