Okay, who broke the planet?

Aries: a knife, lots of stab wounds, especially ones in the face- most likely a rage kill. After they were done stabbing you, they'd start ripping you limb from limb, even if you were already dead.
Taurus: Their bare hands, and they'd strangle you to death. They'd stare into your eyes intensely as they suffocated you to death, maybe even adding in a few dramatic "I got you in the end, you know." phrases while doing it.
Gemini: It all depends on what is convenient for them to use as a murder weapon- they're clever, so they'd figure it out quickly. Most cannibals are Geminis, so they'd probably eat you afterwards. If you really fucked them over, maybe they'd cut off your hands and watch you bleed to death, probably laughing while doing it.
Cancer: They'd take you to the beach and find a secluded area only to tie you to a boulder in the shallows of the beach and watch the tide slowly drown you and sea creatures start to pick at your helpless/crying for help corpse.
Leo: They'd make a whole sport of it- they'd find a bunch of really sadistic, fucked up people on the black market and put you in a pit filled with big cats (especially lions), you'd here "let the games begin!" and a spotlight would come on the death pit as your torn to shreds.
Virgo: They'd make it look like an accident somehow. Regardless, no one would ever find out that they did it, because they'd cover their tracks well enough.
Libra: Similar to the virgo one, but they'd definitely pretend to be distraught by what happened, and mask that they were involved really well...but in order to get you back, they'd get your family, your friends, and other people you cared about to show THEM sympathy, and to be on their side.
Scorpio: Succinolcholine injection after chloroforming the person helpless. (sp? A horse tranquilizer that is extremely hard to detect and basically make the person POWERLESS to do ANYTHING except suffocate to death. It makes all muscles go soft.) and they'd talk to you about how powerless and helpless you were until you died.
Sagittarius: beating the shit out of someone until they were literally an unrecognizable bloody mass.
Capricorn: Shooting someone in the head, mafioso style. They'd want it to be quick and clean, and they'd have organized a team to cover for them, dump the body, and probably hired virgo to hide the evidence.
Aquarius: It'd either be something really strange, whacky, and off the wall, like killing someone in the middle of a play by planning to have a stage light dropped on them, or they'd make an example of you in front of a bunch of their "followers" which they'd most likely have if they were crazy enough to kill.
Pisces: They'd capture you and play surgeon, the whole time ranting and raving about "how it feels" to feel pain as intensely as the emotional pain that they feel. They'd make sure that the kill took a long time so that they had a captive audience for a long time- another reason they'd prolongue it is they'd enjoy being the predator instead of the victim for once.