Here are some dealer's choice variants I've invented. The first few have been posted before, but I've renamed and edited a few of them.
11’s Wild: Any variant. Any combination of cards which add up to 11 can be combined to make a single wild card (e.g. A and 10, or 5 and 6, or 2, 2, 3, 4). (Note that face cards can’t be used for this, and Aces count as 1’s.)
Hearts Are for Sharing: 7-card stud. Hearts are wild, but a player who receives a face-up heart must pass a card to the next live player on their left; upcards stay up, downcards stay down. (Yes, if somebody passes you a heart upcard, you have to pass a card. Like it’ll happen.)
Clubbed to Death: 5-card draw. If your hand contains 1 club, it’s wild; if your hand contains 2 clubs, they’re just themselves; if your hand contains 3 or more clubs, you lose the showdown to any other hand (although you may still try to bluff out the other players). (If all live players have 3 or more clubs at the showdown, best natural hand wins.)
Hi, Jack!: 7-card stud. If you’re dealt a face-up Jack, you must steal a card from another live player. Upcards stay up, downcards stay down. (No, you don’t get to steal another card if you steal a Jack. Nice try.)
Running Wild: Any variant. Suited connectors (cards of the same suit and of adjacent ranks) are wild (note that this means that you will have at least two wild cards if you have any at all).
Bird in the Bush: 7-card stud. After the second, third and fourth upcards are dealt, each player may exchange 2 upcards for a face-down card. Only one exchange is allowed per player per round. Players may exchange two pairs of upcards on different rounds, though. (Note that there are no exchanges after the last downcard is dealt.)
Philanthropy: 7-card stud. After the third, fourth, fifth, sixth and seventh cards are dealt, the high hand showing must give 1 card to low hand showing; upcards stay up, downcards stay down. If several hands are tied for highest, each of them must give a card to the lowest. If several hands are tied for lowest, high hand(s) must give each of them a card. Betting starts at the eldest high hand showing after cards are passed.
Striptease: 5-card draw. After the draw, players reveal cards one at a time, choosing simultaneously, with betting rounds after each set of cards is shown.
Two Solitudes: 7-card (or more) stud. Best all-red hand takes half the pot, and best all-black hand takes the other half. Betting starts at the eldest high all-red or all-black hand showing.
Design Review: 7-card stud. After the last normal betting round, live players must each select 1 or 2 cards which the player to their left must exchange for new cards, downcards being replaced down, and upcards up.
Royal Scandal: 7-card stud. Queens are wild, but if you’re caught with a king and queen of different suits in your hand, your hand is dead. You must reveal all your cards to claim the pot if there is a showdown. If nobody wins, play again, and the winner wins both pots.
St. Valentine’s Day Massacre: Any variant. Hearts are dead, unless you have a flush in hearts, which beats any other hand (the zombies always win in the end!).
Mad Rush: 5-card draw, dealt one at a time with betting rounds. After the 5th card is dealt (5 o’clock), overtime work begins. Players may exchange up to 3 cards, then players must pass one card left, then one card right, with betting rounds after each stage, for a total of 8 betting rounds.
OGIF1 version: After the second round of passing cards, players reveal cards one at a time, choosing simultaneously and with betting rounds (as in Striptease above), for a total of 12 betting rounds!
Bullshit: Each player antes the same amount (e.g. 25 cents). Deal 2 cards to each player (more if there are fewer than 5 players). Player to dealer's left begins, and play continues until bullshit is called. On each player's turn, they may:
a) Fold by tossing their cards FACE-DOWN into the middle;
b) Name a poker hand higher than the previously named poker hand (e.g. King high; Pair of 6's; three of a kind (any); three Jacks); or
c) Call Bullshit.
When Bullshit is called, turn up all players' cards, including folded cards and construct the best possible poker hand. If it's at least as good as the last named hand, the player who called Bullshit has to match the pot and the player who named the hand gets all the money; otherwise, the player who named the hand matches the pot and the player who called Bullshit gets the money. If all players but one have folded, that player wins the antes.
1: OGIF stands for "Oh God, It's Friday!" Fridays can be pretty frantic around our office, because some tests have to run for several days and there's a big push to get them set up to run over the weekend.