Everyone will remember him from his iconic role in Goodfellas and rightfully so. I think he's the unsung hero in that movie when acting against heavyweights DeNiro and Pesci. The movie is in my top 5 of all-time.
I just want to point out his role in Narc was really underrated. The movie has its fans, but mostly went unseen I think. He usually pops up in supporting roles and does his thing, which is always look mean and have a temper but he did it so well.
I remember my uncle rented the 90's thriller Turbulence and I wanted to watch it but he wouldn't let me. Say whatever you want about the quality of that film (most movies set on a plane tend to be mediocre at best anyway) but he gives a delicious performance as an unhinged serial killer.
Smokin' Aces is a large cast of characters in an action film and Liotta has one of the most memorable scenes in an elevator.
Identity is another large cast flick with some twists and Liotta once again is one of the best performances within the film. If you haven't seen the movie, do yourself a favour and watch it. It's basically Agatha Christie's And Then There Were None set in a motel.
Want another flick with an insane cast? Cop Land. Everyone delivers in that one and Liotta once again, stands out among the cast. Stallone gives a really good performance that is outside his comfort zone while everyone else does their usual thing, but Liotta's usual thing is really good.
His voice is imprinted in my brain and that is thanks to Grand Theft Auto: Vice City. My favourite of the GTA games due to the location, music, story and performances. He gives the best voice performances in that entire series.