I love getting smashed but generally think drinking games are lame. However here’s my contribution being as I was on a stag last weekend.
The Best Man had arranged for everyone to have their own personalised beer mat (presumably easy to do if you google it).
The rule was that all drinks had to be on the beer mat at all times unless in your hand. If it was on the table, but off the beer mat then punishment ensued. Punishment= a shot of some sort, though often these were more like three shots in one due to the spanish generosity with pouring shots. Obviously this neccesitates having your beer mat on you at all times.
Seemed to work pretty good, got everyone pretty leathered and obviously there’s always a few who forget their beer mats for breakfast the next morning and end up downing tequila at 10am etc.