Delphine Softwares Future Wars, Operation:Stealth and Cruise for a Corpse were great adventures.

Ooo, BloodNet - half adventure and half RPG

Flight of the Amazon Queen is okay game, it pokes fun of old serial b-adventure movies, but personally I didn't find that funny as such. Bud Trucker was kind of a similar experience for me, not that fun, but playable.

Now, about Al Emmo, I know there's a lot of people who disagree with me, but I found that game pretty horrible. It's an amaterish game with a horrible script and bad voice actors. In comparision to Himalayas free Sierra remakes (under AGDI) Al Emmo is an inferior production in almost every way. But that's just me, I've seen a lot of people defending the game, but that always makes me feel that I played an entirely different game.

Pink Panther in Hokus Pokus Pink
Koala Lumpur: Journey to the Edge

U.F.O.s, also known as "GNAP: Der Schurke aus dem All" - it's certainly one of those adventures hardly anyone has heard about. Great graphics, excellent animation quality, weird humour - an enjoyable experience throughout, albeit criminally short (not to mention pretty easy).

This one looks good:

http://www.kickstarter.com/projects/clickshake/a-small-favor-2d-side-scrolling-adventure-game

Downfall - lesser known game from the dev of The Cat Lady, set in the same universe.
Harvester - the goriest (and the weirdest) game of FMV era.
I have no mouth and I must scream - another great psychological horror, this time set in post-apocaliptic future.
The Space Bar - Strange. Innovative. Certainly deserves more attention than it got in its time.
The Shivah - First game from Wadjet Eye. Short but interesting.

I'll try not to make too long a list ;) These probably aren't that obscure but they are ones that get relatively overlooked and I don't think have been mentioned yet.

Dark Side of the Moon is meant to be a brilliant FMV sci-fi adventure and the little I saw between crashes looked great and very promising, unfortunately it's tremendously buggy on later OS and I could never get it to run properly on my later systems. Needs some gog love!

Zak McKracken and the Alien Mindbenders - admittedly it's Lucasarts and not so obscure, but I'd bet a lot of people haven't played it and really should, as it's excellent and as good as the Monkey Islands and onwards of their catalogue. There's a huge freedom of gameplay and a massive game with a great sense of humour, very happy memories of this one.

Another 'not so obscure but not given much love' title, The Feeble Files. Doesn't always get great reviews but I enjoyed this when it was released moreso than most of it's contemporaries. A proper meaty adventure with hard puzzles and nice locations and story. The only thing I didn't enjoy was the arcade section where you had to win enough credits, otherwise cool stuff.

Starship Titanic is brilliant, an original game designed by the wonderful Douglas Adams and with some very unique gameplay and intelligent but quirky puzzles, just as you'd hope.

Obsidian is another title that gets a lot of love but is very difficult to get hold at a decent price of so I've not played it, would love this one to come here too...

For a slightly more Myst-like puzzle adventure - not my favourite sub-set of the genre - Sentinel: Descendants in Time was a nice one.

Shivers was a lovely Sierra puzzle game, although probably not so obscure either but one I enjoyed more than others from the various Quest series. Although while I type Sierra, I'm compelled to add that all three Gabriel Knight games are excellent, play them if you haven't :)

The first two Dracula games (, [url=http://www.mobygames.com/game/dracula-the-last-sanctuary]The Last Sanctuary) were great against my expectations. I always think they're one big game split into two halves, both of which are equally good. As a side note I didn't like Dracula 3: Path of the Dragon at all, totally different game style and not what I'd hoped for.

Touche: The Adventures of the Fifth Musketeer: another I've not played but gets spoken about as a very similar Monkey Island-like title of good quality by those who have, which is definitely intriguing.

Dead Reefs started off brilliantly but changed into something I didn't enjoy as much later on. The initial feel to it was brilliant however and worth a look for that alone.

The Space Bar would be lovely to see here, one last game here that I've not played but it's a great sounding title which gets good reviews from those who have. A whodunnit in a space bar filled with diverse aliens, one of whom is a criminal you must identify within x amount of game time by searching through their thoughts; the time spent questioning in the bar is timed, the time in the landscapes from their memories isn't.

Spycraft was excellent, a nice spy game that does many unique things and has some excellent and fun set piece puzzles. (just discovered it's on gog, I never knew that! :)

Similar unique adventure experiences that had a great feel to them - although not so much unique, as there's two games doing the same thing - are and, er, [url=http://www.mobygames.com/game/safecracker-the-ultimate-puzzle-adventure]Safecracker. The first was a little more fun for me, the mansion environment was great to explore and find hidden items and safes and solve more interesting puzzles. The more recent game was very nice too but much shorter and with slightly less complicated or satisfying puzzles.

The original Safecracker had a sequel called Traitor's Gate which was pretty nice as well, if a little different in gameplay style with some thief-like action mixed in with the puzzles (in slightly clumsy fashion for occasional frustration). That in turn had a sequel which is not meant to be so good, although I've not played it. There was definitely an English translation, I had it for my old Amiga, one of my first adventure games :) Nice one too, a bit flawed but one of the few games that successfully feels like you're a detective investigating a mystery with some nice gameplay, atmosphere and great setting.

For the same reasons I really enjoyed Post Mortem, at least after the horrible identikit puzzle near the start that was missing around half of the descriptive details needed to solve... The rest was excellent in my opinion, a great choice if you're after a detective title (and one that lives up to that overused noir label).

Ah, long list, how did I know I'd do that once again? Apologies! :)

I'd really like to play the Sierra Manhunter series again. Disliked by some and vastly ignored, but I enjoyed them.

Just finished this one. Short, but great! The art style holds up really well and the story is fairly timeless. Amazing that it was written in the 60s. This and Harvester would be instabuys should they ever show up on GOG. I'm pretty sure Ellison owns the rights to I Have no Mouth..., though, so who knows if it's even a possibility.

Culpa Innata is worth looking into as well. It's mostly based on dialogue, so that might put off many people, but the setting resembles that of Brave New World.

Cosmology of Kyoto is a very cool, very obscure horror-adventure set in a demon-infested ancient Japan. I have never played a game that felt quite so oppressive as this one, though I Have No Mouth comes close.

Also on the horror-adventure front, Barrow Hill is a personal favourite. Highly recommended to those who liked the Dark Fall games (may they return to GOG soon!)

I don't think Ellison likes computers and gamers that much... But he has official website with some contact info. I'm pretty sure he would make some good money putting his game on GOG... Already two instabuys declared, + some more on the wishlist : )
As for the Harvester - it's a really weird game. Could've been so much more if the devs treated it a little more seriously.

I think most of the ones I was going to say have been said now, although Richard from PC Gamer seemed to think Callahans Crosstime Saloon was good:

http://www.pcgamer.com/2011/01/08/crap-shoot-callahans-crosstime-saloon/

Also Neuromancer was well ahead of its time, its time being the late 80s though as I played it on the C64!