I am (mostly) a consequentialist, but I don't endorse killing one to cure AIDS. In general, I don't think it's a good idea to leave those decisions to individuals to make on the fly. That's why doctors have medical ethics codes, and other fields have equivalent codes. Put me down as (mostly) a rule consequentialist.
When push comes to shove, I can come up with a scenario in which I would act to kill one to save many. Suppose a large asteroid is hurtling toward Earth. Its impact would destroy all civilization and possibly the human species and many others. A magnetic field can deflect the asteroid, but an innocent child would have to die.
There is also the famous overcrowded lifeboat dilemma (
http://www.friesian.com/valley/dilemmas.htm). After a shipwreck, several survivors find themselves on a lifeboat. In the stormy sea, the lifeboat sits too low in the water because of too much passenger weight, and it is rapidly taking on water. As the commanding officer, do you order some thrown overboard, to die in the icy waters, giving the rest a chance to live? Or do you do refuse to sacrifice anyone and let the lifeboat go down, dooming everyone?