At one time in the hand your opponent can ask you what you are holding. You have to answer with two cards. i.e. you have to say suit and rank for two cards. It doesn't have to be true. The point of this is to find out who is good at lying. (There'd have to be a way to stop people from just practicing and always saying exactly the same thing. i.e. there'd have to be a way to force people to say something new and unpracticed about their hand.) I think this one would select for people who are good readers / liars.
It can be played with any variant.
One guy plays two hands, and the other guy plays only one hand. It alternates. This would be pretty hard. You'd have to set up the blinds right to keep it interesting. There could be some really interesting hands here. Two speculative hands would be bad, but one made and one speculative hand would be awesome. There would be a lot more extreme situations on the flop or preflop.
As holdem, but during a hand, players can pay extra money to take an extra card into their hand. It should be really expensive - maybe 10bb. It can be done only once per hand.
Making a hand can't be done using more than 2 cards from your hand. (But unlike Omaha, you can still use just one or zero cards from your hand)
as holdem: For a set cost you can require your opponent to reveal one of his hole cards. (Of his choosing). Cost: 20bb
For a higher cost, you can choose the one that is revealed. Cost: 10bb
Any variant: every round, players also bet on how to re-order the hand strengths.
This is a variant of limit holdem. The bet size in bbs is the value of the last card on the flop. So if the flop is AK2 then the bet size for that round is 2bb. If it is AKT then 10bb. Face cards ==> 5bb.
is like "run it 5x" but infinite - reduces variance a lot.
is like duplicate bridge.