Ive killed them with Magnus, Muzzy, Thunderhead, Stingers, Snuffers, and Slick Tricks. My personal choice right now is Slick Tricks. They do an excellent job and are a strong quality fixed blade head. They fly extremely well out of a properly tuned bow.
You can probably kill a deer with about any broadhead as long as its sharp and your shot placement is good. That said, I like to up my odds by using a quality fixed head vs. a mechanical. Too many things can potentially go wrong when bowhunting, I don't want my broadhead to be one of them, especially if my shot is not exactly where I want it. That is when you get in trouble with mechanicals.
People will argue to death over what broadhead to use. It comes down to personal preference really. Fixed heads can fly just as well out of a well tuned bow as field points. Anyone saying they can't has never shot a well tuned bow.
My suggestion is get a good quality head (fixed or mech), and much more importantly make sure your bow is tuned properly. A mechanical head used as a band-aid for a poorly tuned bow will stack the odds against you.