The caster the original predator had is still my favourite. The iconic "crack" sound it made was just awesome, & has never been matched in my opinion. In a tie for second are The Wolf & Predator 2's hunter. The Wolf's casters, visually, looked fantastic, but had a weak & unimpressive sound effect.
The AVP casters were horrible on all fronts. The one Scar used looked like a giant cannon, not very predator-like at all. You could actually hear the operating system used to maneuver the mount for the gun...ugh. Not to mention how easily it was knocked off his shoulder towards the end...like it was tacked on, how ridiculous.