My favorite game of all time might as well be Monkey Island 2: Le Chuck's Revenge. It might be the wittiest and most fun experience ever. The music is great and the graphics are outstanding. Characters are lovely (even LeChuck himself) and the story has depth.
I have two favorite characters in Monkey 2. One is the Voodoo Lady that always have a way to tell Guybrush that he's going to die, and there is but a small hope. The other is Stan, that would survive anything, come jumping up from the grave trying to sell you toothpaste.
When I played this the first time, I was really scared of getting arrested on Phat Island. But I had forgot that you can't die in Monkey Island games, and getting arrested is not so bad.
Hardest puzzle for me was probably the catalogue index in the library and finding the right books. I took some help from Walkthroughs (before internet those where published in computer magazines) and got past the trickier parts.
Make sure you replay this through the HD remakes that have been coming out last years. It is still as good as it was 20 years ago.