Some of mine in no particular order.
Adventureland
The first Scott Adams game has a very classic design. It’s a treasure hunt through a forest and some caverns, with a bit of magic thrown in and a lot of random things that can go wrong. As a kid, it was one of the first adventure games I was able to make progress in on my own, though my dad already considered it uninteresting compared to the graphic splendour of stuff like Wizard and the Princess. However today, I don’t really enjoy playing Wizard and the Princess, but I do enjoy Adventureland. The game has an elemental adventure quality befitting its name
Strange Odyssey
I still haven’t played all the Scott Adams adventures, but this is my other favourite. Relatively speaking, Adventureland comes across as friendly, whereas Strange Odyssey is hostile and properly alien in feel. Again, this is ultimately a treasure hunt, but the treasures are on different mini worlds, reachable through a portal in an abandoned spacecraft. Each world is very dangerous. You might step through a portal into an incompatible gravity field and be crushed immediately. I really like the sense of unpredictable danger and mystery in this game. The minimal prose works well because the worlds are more threatening without explanation.
Wishbringer
The only Infocom game I was ever able to make major headway in on my own, though that’s not the only reason I like it. I love the transformation of the town and its atmosphere, and the black humour attendant upon the transformations. I find the game creepy and mysterious, exciting but threatening, and the puzzles are doable. A great spooky fantasy game.
Suspended
The first Infocom game I ever played. I didn’t achieve much (again, I was probably eight years old) but I kept playing the part I could do again and again because I love the chilling atmosphere. I get creeped out when my robots are dispassionately reporting on the arrival of the humans who have come to turn me off. Also there’s the whole business with the robots themselves, named after their propensities (kinda like the Smurfs). I like moving their counters around on the real board, studying the board and thinking about what might be in different locations. I’ve still got my original copy of this with the big frozen face prop.
Lucifer’s Realm
Ken and Roberta Williams teamed up with the guy who did the graphics for Transylvania to produce a game about dying and going to hell, where Hitler is taking over. This Apple II game is scary, but somehow a better word is freaky. One of the puzzles involves trying to get past the Rev Jim Jones (he’s guarding a door). Lots of caverns, abysses of screaming souls, blood and freaky graphics. This game tried to maximise the graphics real estate by using the whole screen for graphics, then hiding the picture for the text interface as soon as you started typing.
Marika the Offering
This is my favourite one room game from recent times. You play a young woman barricading her room against a vampire. It’s not that I’m opposed to one room adventures which are conspicuously adventurey - that is one of the joys of adventure games - but this one is probably not, and its natural quality, earnest tone, the sense of urgency and the neat way of giving you clues when you die all add up.
Theatre
Just finished playing this the other day, but I would say it’s one of the best modern spooky games done in a classic style. After leaving your pager in a theatre, you become trapped in there and get involved with an ancient plot. This is quite a big adventure, but with no terribly abstruse puzzles until near the end. I found it was a game where you could keep circling areas already visited and become unstuck as a result. I hate games where I circle diligently, only to find out the solution was a real mind reading job that wasn’t actually to be ‘found’ anywhere, and wasn’t sufficiently suggested. A good atmosphere and good puzzles in this one. (In similar terrain, I also tried Anchorhead, but I find it too hard and abstruse, and it was another experience for me where the walk-through destroyed my interest in the game, resulting in me quitting.)
One Eye Open
A little buggy in its current state for my tastes, but a great purveyor of a very contemporary style of horror. Psychic experiments go awry, moving you through parallel and alternate realities in a hospital ala Silent Hill. Lots of good creepouts, shocks and guck.
Aotorea
Just don’t make me spell its name… A good and earnest G-rated adventure, very well written, quite action packed in spite of relatively hefty wordiness. The delivery has the kind of grace+flow that tends to make a game of any genre stand out.