I play quite a few but mostly Texas Holdem, mainly because that is the preferred game for many players, the registration to any size game happens to fill very fast and you could be in and playing within a minute.
Other Variants I can play are Omaha, 5 Card Draw, Stud, and Razz. The time it takes to fill some of these games can be a little slower, but I find Omaha is getting more popular than it was a few years ago.
I would recommend that anyone trying out new formats that they are not used to, To buy-in first with Play Money chips, so they can get an idea how the rules work, before they start to lose
real money, Just like Texas Holdem it can take a lot of practice before you fully understand the different Variants of the game.
When the fun Stops, STOP!