1) The It's It Scenario
The LHC creates a wormhole, through which beings from the future send back a new and improved It's It bar. It is found to be extremely delicious.
2) The Buffalet Scenario
Similar to the strangelet (strange matter) scenario, except in this case a particle is produced that has crazy quantum properties that allow for the possibility of a non-run-on sentence consisting of only the word "buffalo" 50 times in a row. This "buffalet" particle starts a chain reaction that converts all particles in the solar system to buffalet particles. The buffalo phenomenon becomes even more awe-inspiring and the world is a better place as a result.
3) The Stranger Scenario
Also similar to the strangelet scenario. Basically what happens is that the LHC produces something amazing that unlocks the secret to the universe. The physicist running the machine at the time is so excited about this finding that he bursts into a nearby office unannounced...and walks in on his colleague giving himself the stranger. This moment is so awkward that it causes a wave of awkwardness that sweeps across the planet. We don't die, but things are extremely awkward for the next 100 years or so until the awkwardness evaporates.
4) The Bad False Vacuum Scenario
Ok, this one sort of blows. Some scientists think that we may be living in a "false vacuum" and that a "true vacuum" with lower potential energy exists. The energy of the collisions produced by this particle collider may be enough to overcome the barrier needed to knock us into the "true vacuum" state. A bubble of this new vacuum state expands through the universe at near-light speed, killing everything in its path, including all of us and all other lifeforms in the universe, except maybe cockroaches. Whoops. Sorry, aliens - our bad.
5) The Good False Vacuum Scenario
A bubble of superior vacuum cleaners (probably the Oreck XL21 Titanium Series) sweeps through the entire universe, replacing all the crappy vacuums in its path. Aliens from far-away galaxies thank us for making their floors cleaner than they ever imagined possible.
So if you're keeping score at home, the odds of us all being killed by this thing are now estimated to be only 6 out of 11, or about 54.5%. Still not great, but the fact remains that doing these experiments is inevitable because it is natural human instinct to want to smash stuff into each other and see what happens (hey, that's how you were born!). My advice to you is to not sweat the small stuff, like whether or not you're about to be painfully spaghettified by a black hole or blown to pieces by an expanding vacuum bubble of doom. There are a lot more important things to worry about, such as the relationship status of these two "celebrities" that nobody has ever heard of. Party on, Wayne.
*Thanks to Jon Frank for the original ideas for scenarios #1 and 3.