Scientists still think that an apple made of anti-matter would hit your head (never mind the consequences), but they are not certain, so they plan an experiment called AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) at CERN to test, which way a beam of anti-hydrogen atoms would be deflected by gravity.
This is not an easy task. Every anti-atom must be made in a particle accelerator, making it probably the most expensive substance one could buy (estimated $300 billion per milligram). But the real problem is containing the neutral (non-charged) antimatter, since as soon as matter hits antimatter, they annihilate each other and turn into energy. Using charged anti-protons for this would solve the container problem, but since the electromagnetic force is many times stronger than gravity, the effects of gravity on the antimatter would not be observable.
If antimatter were to behave opposite to matter regarding gravity, that could explain the missing antimatter in our universe, since it would not be attracted but repelled by the observable matter.
Read more at the physics arXiv blog.
The crazy bit
Applying Maxwell’s equations in four dimensions, one cannot distinguish an anti-proton from a proton moving backwards in time. So you could say that the creation of an anti-particle in an accelerator, from the anti-particle’s perspective it’s its destruction, and the seeming annihilation with a particle was its creation.