Eric the Unready would be my first choice (a text-adventure game released in 1993). It's still, by far, the funniest game I have ever played, and is the ultimate geek-culture parody (mainly being a fantasy spoof, but there's also plenty of sci-fi references, as well as movie nods, and Monty Python humor, etc).
A second choice would be King's Quest VI: Heir Today, Gone Tomorrow (released in 1992). I know there's tons of "better" point-and-click-adventures out there (all of which I love), but KQ6 has always been at the top of my list. I played through it multiple times back when I was a wee nine-year-old lad, and still remember most of the puzzles fondly.
My last choice (because I can't settle on just one) is Bad Mojo (released in 1996). You're a cockroach . . . it's as simple as that. Bad Mojo is dark, gritty, weird, and mostly pointless; but I was in awe of it's absurdity the minute I laid eyes on it.
. . . methodical, exacting, and worst of all, patient.
Jetfighter 2 might be considered a classic by some but I'm not sure just how popular it actually was. Such a great dos sim way back when. Can be found on myabandonware.com if anyone feels the need to have a blast from the past. I highly recommend your own music though :P