Gotta love those Space Quest games! You haven't really lived until you've played Astro Chicken in a space diner.
And traveling back to Space Quest 1 with EGA graphics.
There is also this scene where you have to free up memory on some machine by throwing applications in the thrash can (erm toilet) [1]. The first time I made the mistake to trash the SQIV icon, which throws you right back to DOS. Of course, I hadn't saved for a while.
[1] http://www.mobygames.com/game/dos/space-quest-iv-roger-wilco...
There's also some great Space Quest games made by the community, such as Space Quest 0, Space Quest 2 Remake, and Vohaul Strikes Back. Worth checking out for any SQ fan.