The old school 3d Dungeon Crawlers, the ones where you actually had to feed your party food and water so they wouldn't die? A couple excellent examples of these would be
1. Dungeon Master
2. Chaos Strikes Back (Dungeon Master Expansion)
3. Dungeon Master 2: The Legend of Skullkeep
4. Anvil of Dawn
I find these types of games to be very fun. Most of them were based on ADD rules, which made them even better still. Anyone agree?

I remember playing Dungeon Hack and Eye of the Beholder back in the day, though I never managed to finish either one.
I'm also a big fan of the old first-person party RPGs in general, especially Might & Magic 3, 4 and 5.
I'm tempted to buy the newly-expanded Ishar collection, because something like that is right up my alley, but I have trouble with the combat, so I'm not sure if it's worth struggling through.
Doesn't Ubisoft, with whom GOG has a deal, own the rights to both the Might & Magic titles and SSI's back catalogue? HINT HINT

I played the Eye of the Beholder games (badly), they were good but quite hard to get into. My mapping skills werent the best as well!
I suppose in a way Ultima Underworld 1+2 would count, since you have to eat, but they have a very different style.
If you like those by the way you should look into trying Mordor: The Depths of Dejenol. Theres no need for food or things like that, but it's a great dungeon crawler (I suppose it's more of a rogue-like in some ways).

WIZARD NEEDS FOOD BADLY!

I remember playing Planetfall (Infocom) on the Amiga back in the day. Not exactly 3D. Not even 2D, in fact. It's a text adventure. But it was a dungeon crawler of sorts, in that you needed to draw a map in order to find your way around. Ah, the old days of hand drawn maps on squared paper (?), each "room" a 3*3 square with little notes and stuff. Those were the days...
Anyway, the food and drink issue was especially important in that game, since there was only one food and drink dispenser, and you could only carry one canteen of water, and one meal. This put a sharp limitation on how many "steps" you could take away from the dispenser and still get back before you died of thirst or hunger.

Arx Fatalis is a more recent example of a dungeon crawler where you have to eat in order to live. Granted, it doesn't have a party but it still uses the same mechanics of food and water.

Yeah, when I came on this morning and saw that the Ishar collection had been expanded to include the entire series, I added it to my wishlist right away. You are right about Eye of the Beholder as well, those were excellent games, but I never finished any of them.

Did anyone play Thunderscape by SSI? So underrated. I bought that game new for a dollar back in the day, and I still love it. It's a little campy, and the game mechanics are not all that great, but for hours of hardcore dungeon hacking, monster killing and awesome music, you could do a hell of a lot worse.

You bring back fond memories sir!
I remember two things about Eye Of The Beholder.
1. There was a clue word I discovered during my adventure 'tropelet'
After hours of pondering, my Girlfriend (now wife) immediately said 'oh that's teleport backwards'. Yep, she made me feel an idiot!
2. My mate accidentally deleting my save whilst I left the room to put the kettle on.
How I laughed.... not.

Ouch.
I mostly remember getting my arse handed to me on the first few levels and that hole in the wall which turns a normal dagger into a guinsoo (sp?) knife.

Betrayal at Krondor required your party to eat and sleep. You also had to repair armor. To top it off, there was almost no magical equipment. A sword was a sword--maybe not designed for your race and therefore you used it at a disadvantage, but it was just a sword.

I don't remember a memory leak, perhaps I was lucky, or just got a later edition which had corrected the problem.
It did have many other bugs though, I remember having a problem with certain events occuring, such as the changes in the room with the gem underneath Castle Brittania. I remember a point early on where an Imp was supposed to be there, but nothing had changed. I had to restart the whole game.

I'm sure that was in Nethack. Man, Nethack is awesome, just like Dwarf Fortress.

That is actually like a line from the original Gauntlet. Awesome game too, most definitely a classic of times past.