Hi,
I believe I saw a first person decapitation using a mace during a gameplay video on ign.com, so it should be possible. It might zoom out to third-person for the fallout-esque kill but I don't remember that clearly :S. In any case, the perk description does not suggest a discrepancy between swords/axes/maces, so it should work with maces as well...
Sorry I can't give any more certainty. I think you can get decapitations with any weapon though.