Welcome to the best animation in OVA category! There have been many OVAs out, but... oh, it looks like no one cares about this anyway, so let's just go to the results. :notrust
Total of 34 votes. Hellsing Ultimate wins with 13 votes, and no other OVA came close... the closest is 7 votes.
So yeah, congrats Hellsing Ultimate, I guess? :confetti