Ghost in the Shell: Standalone Complex for PS2.
For starters, Ghost in the Shell for the original Playstation is one of my all-time favorite games, the ultimate first/third person shooter, like a cross between Descent and Jumping Flash.
Secondly, I had played a demo of SAC, and it was bloody awesome. The best feature is the cyber-jacking, where you can remotely hack enemies and control them. I would hack an enemy close to me, then use him to mow down his compatriots, who were really rather quick to react to my little ploy, leading me to try different strategies to make the most out of my little meat-puppet.
The problem is, it turns out the cyber-jacking is pared down considerably for the full game. You can only hack SPECIFIC enemies at SPECIFIC times for SPECIFIC lengths of time for SPECIFIC purposes. At one point, I found (after much trial and error) that I was supposed to hack an enemy on top of a crane, during which time I'd have five seconds to take down a sniper on a guard tower. There's no strategy, it's just being led by the hand.
The game's most open feature did a 180 and become its most restrictive. That was just disappointing beyond compare. I traded that damn thing back in practically the next day. Fortunately, even though it was a trade-in, I still got 75% of my money back, so it wasn't that big a loss.