For each drinking game, we're just listing the absolute best rule of the bunch. For the whole set, click through on each link. (Unfortunately, there was no way I could test-drive all of these; I kind of wanted to keep my liver.)

General:

Drinking Game with the Sci-Fi Channels Original Movies (by Joanna Lopez, associatedcontent.com)
Best Rule: four sips if the movie looks like a poor person's version of the latest popular movie playing in theaters.
Likelihood of Intoxication: Relatively High

The Scifi/Action/Disaster Movie Drinking Game (posted by oblivion)
Best Rule: Evil clown/mime/street performer (Because, really, I had no idea that happened with any sort of regularity in sci-fi and action films.)
Second-Best Rule: Leading man named after verb or mineral (Because now I'm trying to think of an example and can't . . . You know, this game has some odd rules.)
Likelihood of Intoxication: Moderately High, especially if the plot involves a guy named Hunt Quartz preventing a syndicate of mimes from setting off their hurricane-causing doomsday machine

Spot the Scifi Cliché! A Drinking Game(by Charlie Jane Anders, here at io9)
Best Rule: The hero has a miraculous gadget (which may rhyme with ironic brew diver) allowing him to get out of literally any difficult situation with no hassle.
Score: Minus 10 points.
Drinking game: Make yourself a sonic screwdriver out of orange juice, vodka and ultrasonic vibrations. Drink the whole thing in one go.
Likelihood of Intoxication: Probably highest if you're watching a show that may rhyme with Proctor Glue (Speaking of which . . .)

Specific:

Doctor Who - The Drinking Game! (by Simon Oxwell)
Best Rule: If you see something of which 1970s anti-violence crusader Mary Whitehouse would disapprove (This is a drinking game designed for the classic series, by the way.)
Likelihood of Intoxication: Moderate, depending on which Doctor it is and how many Daleks are present.

The Batman Movie (1966) Drinking Game (Sky of Blue's Hoosier Journal of Inanity)
(Can I just say how pleased I am that someone's made a drinking game for this movie, considering how much it pretty much cries out for one?)
Best Rule: Now, here's the REAL kicker. At one point in the movie, Robin asks Batman, "You risked your life to save that riffraff in the bar?" Chug ONE ENTIRE BEVERAGE upon Batman's reply of, "They may be drinkers, Robin, but they're also human beings ..."
Second-Best Rule: "Under this garb we're perfectly ordinary Americans."
Likelihood of Intoxication: I'm going to say "Pretty High," because according to the creator of the game: "With what we were drinking, no one remained upright much past Rule 5." (Although now I just want to know what they were drinking . . .)

Drunkgate: Stargate Drinking Game (for Stargate: SG-1)
Best Rule: The team has to impersonate deities. (This includes if they are recognized as such but choose not to carry out the impersonation.)
Second-Best Rule: There are trees. (Basically, I think this rule should be added to any and all drinking games.)
Likelihood of Intoxication: Extremely High, from what I can tell (But only if you follow all the rules, of which there are about a million)

The (Original Series) Tomorrow People Drinking Game (by Beth Epstein, with submissions by Heidi Howard, Amy Houghton, and Maria Sloughter)
Best Rule: A trend in fashion or pop culture turns out to be an insidious alien plot.
Likelihood of Intoxication: Extremely Low if you follow the rule at the start of the game: "Tomorrow People don't ingest anything that will affect the functioning of their minds. Alcohol affects the mind. Therefore, Tomorrow People don't drink alcohol. This game is meant for root beer, juice, or other soft drinks, or you could use M&M's (1=sip, 2=gulp, use snack size/halloween size bags for whole drink— or two really big handfuls)." (I figure this is one of those instances in which rules were made to be broken, though.)

300 Drinking Game (SuperHeroHype Boards)
Best Rules (Aka, the only rules): Every time the word Sparta or Spartan is mentioned, you drink. Or if you want to get really plastered, you have to keep chugging during all the slow-mo.
Likelihood of Intoxication: For a game with only two rules, I feel the odds are pretty darned high.

The Battlestar Galactica Drinking Game (by Denise Martin, Los Angeles Times)
Best Rule: Sneak a swig... Every time you wonder why more people watch "Lost."
Likelihood of Intoxication: Moderate.

Supernatural Drinking Game (by Lsketch42, via YouTube)

Best Rule: I don't know that there's a best rule here, as I couldn't really get past the polka music and The Chicken Dance. That being said, I admire anyone who condenses an entire show down to the moments when you ought to be drinking.
Likelihood of Intoxication: If you watch the drinking game video, you're probably just going to have to chug for a couple minutes straight, so I figure your odds of being buzzed by the end are up there. (You will have also endured a few minutes of the aforementioned Chicken Dance music, so I think you've earned the buzz.) If actually watching the show, with all the extraneous plot and stuff, your chances of intoxication plummet pretty severely, I think.

KryptonSite's Smallville Drinking Game! (via KryptonSite)
Best Rule: You count more than a five second awkward silence between Clark and Lana.
Likelihood of Intoxication: Pretty Darned High
(Then again, here is another, which gives you new rules every time you refresh the page.)

The Star Trek Drinking Game
Best Rule: A newly discovered planet is "Much like Earth"
Second Best Rule: Kirk violates the prime directive (Mostly because I thought it said "detective" for a minute. Now that's an episode that should have happened.)
Likelihood of Intoxication: Pretty High (I'm interested to see how well it holds up in the movie coming out next week.)

Heroes: The Drinking Game (Miss Geeky)
(But you can find others here and here. As well as about a hundred other places.)
Best Rule: Mohinder saying "evolution", "mankind", or "cure". (I think you could pass out on this rule alone.)
Likelihood of Intoxication: Pick any one of the games and you can get really wasted. Combine all of them, and you're dead.

The rules are simple. Take a drink of your favorite beverage whenever one of the following occurs:

• A proton crosses the border between Switzerland and France.
• A magnet quench in a superconducting magnet causes all the liquid helium to boil away.
• A Higgs boson is detected (2 drinks).
• Scientists learn the secrets of the universe and go insane (2 drinks).
• A miniature black hole forms (2 drinks if it absorbs Switzerland).
• Strange matter is created (weird, unusual or eccentric matter doesn't count).
• A petabyte of data is generated.
• Someone sings the chorus of the LHC Rap.
• The Super Proton Synchrotron reaches 300 gigavolts (2 drinks if it hits 400 GeV).
• The Compact Muon Solenoid finds something that completely alters our understanding of the fundamental forces of the universe.
• Flight 19 suddenly appears over Geneva.
• Particle superpartners are found to have natural supersymmetry.
• An intern confuses muons with gluons.
• The experiment goes awry and someone ends up with superpowers.
• Aliens show up and make us turn off the LHC before we implode reality.
• Scientists go back in time (2 drinks if they create a paradox).
• Someone says "Big Bang."
• Particles crash into each other (2 drinks if there are Batman-tyle visual sound effects, like "Pow!" and "Zap!" when it happens; feel free to construct your own).
• Someone says, "What's a hadron?"
• Scientists access another dimension (2 drinks if that dimension is occupied entirely by Donna Summer impersonators; 3 drinks if denizens of said dimension eat the scientists; note that these two conditions are not mutually exclusive).
• Someone on TV questions the amount of money spent to build the LHC.
• Someone on TV worries that the LHC will destroy the world.
• The world ends (drink whatever you have left).
• Scientists prove string theory (3 drinks because we'll all pretty much have to take their word for it).
• Someone uses the term "beam pipe" in a pickup line.

You'll be much less confused by all of that jiggery-floopery about who time traveled when, and which stocky robotic dude is named Chrome Marty, if you follow this drinking game to the letter. You need shots of some kind of liquor, preferably bourbon or vodka. And some beer. Tell all your friends to do this in their own homes, and we can help the show deliver gang-spanking ratings to the suits at Fox.

Take a swig of beer every time:

• Summer Glau tilts her head to one side and stares intently.
• Thomas Dekker looks at the ground like a whipped puppy.
• Brian Austin Green punches a wall or some other surface.
• One of the high school kids looks at Summer Glau funny.
• We see Lena Headey exercising.
• Someone mentions "The Turk."
• Lena Headey has a bad dream. (Three swigs if she decides to take action based on it.)
• Someone tells John Connor that he's not the heroic "Future John" yet.
• Summer Glau repeats something someone has just said to her, in a robotic monotone.

Drink a whole shot every time:

• Sarah Connor has a voice-over where she quotes from literature or history, or talks about wise old sayings.
• Summer Glau says something dorky, like "Thank you for explaining." Or tries to talk like a cool kid and fails.
• FBI Agent Ellison reads, or quotes, from the Bible.
• A Terminator other than Summer Glau is in a scene, and doesn't commit any violence.
• John Connor has a surrogate-dad moment with Brian Austin Green or his ex-step-dad.
• John Connor decides to prove he's a hero by doing something completely half-cocked.

Drink a healthy swig of beer and a whole shot whenever:

• Another Terminator gets its skin ripped off, or actually gets deactivated, but Summer Glau walks away without a scratch.
• There's a discussion of whether Summer Glau has a soul.
• Sarah Connor screams at her son, or cries.
• FBI Agent Ellison starts acting like he believes in the Terminators.