My all time favorite horror movie has to go the my beloved 1974, Black Christmas. It was the inspiration for many other horror films, including Halloween! It defiantly doesn't get all the love it deserves for basically starting the whole slasher craze.
Now, my favorite killer is a bit harder to decide, but I'm going to have to go with Vincent Sinclair from House of Wax (2005.) The movie is amazing in itself, the plot and backstory of the brothers is heart-wrenching to say the least (Of course, they are killers, so I don't feel too bad, but Vincent's motives are so sad T.T)