I 'd have to say Centurion in hand-to-hand because of their wicked size and speed, not to mention the long, razor-pointed fingers that would pry into and dismember the T-800 before it had a chance to use it's immense strength.
I realize, however, that if it were an armed fight, and the T-800 had one of fancy plasma rifles as-seen in T2, it would win easily.
(I just wanted to see the BSF goer's stance on Cylon vs. Terminator after Googling it and not being happy with the results)