One of the very first LucasArts adventure games come to mind;
Loom. It had quite a unique gameplay at the time, and probably one of the earliest music games, where you have to replicate certain tunes you hear throughout the game using a sequence of musical notes, each making up for a different spell. It's a bit on the short side, but thoroughly enjoyable on the Expert level. And the talkie version has some funky, british voice acting.
Aside from the usual Sierra/LucasArts games, there's some other less known ones, like
Sanitarium; a great horror-themed adventure. The game has a very spooky atmosphere, starting of at a sanitarium full of sick people and people banging their heads on walls, then progressing to other more weird locales. The main character is pretty messed up too, his head all bandaged up and having no clue of identity (at first) or how he got into this situation. Gameplay-wise, it's pretty easy and straight-forward with puzzles that make sense and no illogical item use and such, making you focus mostly on the gripping plot and numerous (3 disc's-worth) cutscenes.
Also the very humorous, if in the same vein of the Monkey Island's,
Simon the Sorcerer 1 & 2. These were quite fun, with humorous writing and witty dialogues between the protagonist and the myriad of wacky characters in both games.
May I also suggest some quality freeware adventures? There's this top-notch one called
No-Action Jackson. Very reminiscent of Day of the Tentacle in both style and gameplay. Even the main character looks like Bernard. Quality adventure that's actually free.
There are probably more I could be adding later, but these should keep you busy for a while. =)
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