Any good quality broadhead will do the job. I've taken many, many birds with the same head I used for deer in the same year. It is a good starting point to just use the same head and set up your first season after Turkey. But, a good mechanical is what I have been using the last couple of years. The wider cut and the shock of the energy to open it in the bird seem to be a good combination to pinning them. I like Innerloc EXP's, but NAP Spitfires, Rockets, Wasps, are some other good ones I've had excellent luck with as well.
ABC/Sonic has come out with one that looks pretty good too called the Turkey Tearror. They are also manufacturing the same one for Fuse called the Strut Buster. I may just give them a try this year as well to experiment a little.