Monkey Island 2: LeChuck's Revenge will always be among my favourite LucasArts games. The sequel to The Secret Of Monkey Island was where things got a lot more Pythonesque. But it's a lot more than just a treasure hunt and a barrel of laughs, it was very clever for its time.
The music in Monkey Island 2 is still fascinating. Walking through different areas in the first town, for example, will seamlessly transition the music into slightly different version of the same track. Heading inside the dry cleaners will bring out some trumpets, while Wally's cartographer's studio gives you strings.
It's also the entry in the series where the gags are at their peak, especially for the curious player. If you try to "pick up" the ship charter woman you'll get a whole bevvy of cutting rejections, and if you go through all the colour options when talking to Herman Toothrot, there's a great lesson in philosophy to be found. There's even a couple of Star Wars references for good measure, as if you needed any other reminders that this was a LucasArts game.
If you want to play it, the remake a few years back has flavours of both old and new and is well worth your time, even if the game doesn't quite stick the landing.