One player goes first. Using mental telepathy, s/he tries to predict the color of the card about to be turned over If correct, s/he continues; if incorrect - drink.

If correct three times in a row, the player can make a rule concerning procedure for the game. Interesting rules are:
"Can't say red"
"Can't say black"
"Tap head before drinking", etc.
As always, be creative.

Of course, if some is caught "violating" a rule, s/he drinks. But be sure not to break the rules while enforcing them.

Beerhunter
How to play it:
The rules are so easy, a drunk person could understand. All you need for this game is a sixpack, a box, and people to play it with you.

Take one of the cans and shake it. Now I don't mean just shake it, I meanSHAKE the sucker! Till it's about to blow up. Then put it in the box with the other cans and mix them around (one person not looking) and then switch them around again (the other person not looking) Basically, nobody knows where it is.

Now, one person picks a can, holds it to his/her head at an angle, and opens it. If it's not the one, s/he has to drink it. If it is the one, s/he gets a wet head and you can start all over or whatever. Then, if it wasn't the one, the next player takes one and tries. etc.

Drink Or Dare
How to play it:
Everyone is familiar with the game "Truth or Dare"... and everyone knows the Truth half is lame. The whole point is to Dare other players to do ridiculous stuff. Therefore, replace the the "Truth" option with "Drink."

When electing not to take a dare, the victim instead takes a shot. In no time, everyone is drunk and ready for some absurd dares.

Beer Dice
How to play it:
Roll two dice. Anything that adds up to six (i.e. 2-4,5-1) or has a six in it (i.e. 6-1, 6-2, 6-2, 6-3, 6-4, 6-5), you drink a "good" gulp of beer.

Any time you roll double 2s, 4s, or 5s you drink that many (2, 4, or 5) "good" gulps of beer (You can modify this to just one "gulp" on doubles).

If you roll double 3s you are penalized twice, for getting doubles and adding up to six. Thus four "good" gulps (or 2 if you play the modified rules).

The killer is double 1s or double 6s. For this you do a SHOT of your favorite poison (i.e. JD, Southern Comfort, tequilla, etc).

Lastly...you continue rolling until you get something that you don't drink on (i.e. 1-2, 1-3, 1-4, 1-5, 2-3, 2-5, 3-4, 3-5, 4-5). If you roll the dice off the table, you are also rewarded with a gulp of beer.

Pranks
"Stag night pranks can be great fun but don't let them get out of hand"

Cross Dressing
Having got the groom absolutely legless, take him back to his room and put the unconscious lump to bed. Then proceed to completely empty the room of all his personal possessions, leaving only his travel documents (optional) and a previously bought dress with matching shoes.

How, make yourselves scarce and leave him to find his way home... wearing nothing but the sexy black mini skirt that you picked out for him 3 weeks ago! Remember to pick a dress that will match his eyes, otherwise it could be a bit embarrassing couldn't it? Oh yes, he's going to hate the lot of you for this one!!!

Backdraft
Before jetting out to your chosen city, distract the groom sufficiently for some one to tamper with his suitcase. Once in the suitcase, replace all the groom's trousers with one solitary pair that have had both cheeks cut out! For underwear, leave nothing but a pair of frilly knickers/G-string/you get the idea. Remember to keep your suitcase well hidden upon arrival, because as soon as he finds out what's happened he'll be pulling on your 501s as quick as he can. Again, if you can set this up before all departing the hotel (and he's the last one to leave, so has no choice) then it's a sure thing to drop him right in it!

Wrong Stripper
If the groom is not of a particularly aggressive nature (i.e. is not going to stick your head up your own arse for doing it), arrange for him to have a final bit of action in the form of a stripper. Watch as he laps up the attention the woman is paying him. Watch his face as she slowly rubs oil into his chest. Watch his excitement grow as she handcuffs him to the chair. Watch him go absolutely mental when he finds out the stripper is actually a bloke!

This one is for highly recommended for the twisted of mind, though it takes a good act to carry off the gender swap (unless he's had 12 pints, in which case John Prescott would probably be able to fool him!)

It's a Jungle in There
Leave the Groom bemused that nothing actually happened during the Bachelor Party, only to find that, upon his arrival back home, his living room lights are all on... Lights that are fuelling the growth of one-inch-high Cress, planted only two days previously in a sodden area of carpet by you, his loving mates! For that personal touch, distribute the seeds in such a way that a message is written in the emerging flora.

CAUTION: Do not undertake this gag if he shares the house in question with his loved one. Unless you're tired of having testicles anyway, that is.