The one and only, Wolfenstein 3D, pioneer of first-person shooters, celebrates its 20th birthday this month. Thus Bethesda has provided us a browser version of the game, so people who have never played it can have a taste. And on the other hand, real old-schoolers can reminisce their lost youth and cry a little bit.
The game can be found here: http://wolfenstein.bethsoft.com/
Have a nice war, mr. Blazkowicz!