Ah, I'm a big boardgame fan, I have an old group of friends that always play these games when we get together:
Die Siedler
We have the German version with all the 6 player expansions etc as the Brit one didn't come out till a little later, I have the Dutch version, and bought the 'Alexander/Cheops' expansion in Berlin last September...great stuff. Even played at a tournament of this in London
Dungeon Quest
A vintage Games Workshop game from early 80s based on an old Swedish game called Drakborg (or whatever the Swedish for 'Dragon's castle' is)
Axis and Allies
One of my personal favourites - very involved, takes a long time
Shogun
Classic strategy game set in Japan. How could anyone play that heap of bleep, Risk, is beyond me.
Scrabble
I love it, but none of my friends do. So I play it about once a year :-(
Blood Bowl
Another classic played with old schoolfriends when we get together. A great game, but you don't really have time to play tournaments of this when you get to adult life. There's an excellent Java version of it called fumbbl or something - haven't played it in about a year
Escape from Colditz
Another classic, but a lot of my friends don't like it. Played rarely
Space Hulk
A GW classic, play it once a year or so.
Chess
No introduction needed
I'm sure there are plenty of others I've forgotten
edit:
Yep, I forgot...
Starfarers (by Klaus Teuber of Die Siedler fame)
Brittania
Blood Royale
El Grande