Well, not really a cheat but in some version of Wolf 3D
 press M on the opening screen and you get a jukebox...
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 Ted cheat (on command line):
 wolf3d /tedlevel 0
 [where level you want is 0 (level 1) through 9 (level 10)]
 
 Cheat mode option (on command line):
 wolf3d -next [v1.0]
 wolf3d -goobers [v1.1+]
 
 Cheat mode activation:
  Control-Tab-Enter [v1.0]
  Alt-Shift-Backspac [v1.1+]
 
 Cheak keys (press TAB with key):
  B Change Border color
  C # of doors, actors, food, ect
  E End level, advance to next
  F Find x, y coordinates and angle of you
  G God mode!!!
  H Hit yourself
  I Add items to you
  M Memory useage
  N Clipping toggle (walk through walls) [v1.0]
  O Overhead map [v1.0]
  P Pause game
  Q Quick exit [may crash sod]
  S Slow-motion mode
  V Add VBLs [v1.1+]
  W Warp to level of choice
  X Add extra stuff [v1.1+]
 
 The I L M keys at the same time will get you Everything.  Though you
 might say "I'll lose all my points..." well, that's no longer true.
 I have found a way to keep your points!  But you must do it extactly
 like this:  At some point in the game you HAVE to press TAB E to end
 that level and advance TWO levels, not one.  You can also just go back
 with TAB W if you want to finish things in order.  Once you've done
 that, you can (with your wonderful score!) press I L M and you'll lose
 everything. To get it all back, just press TAB W and type the level
 that you were on (or whatever level you want) and you will get ALL
 your points back. A couple of other cool things you can do is TAB T
 and look at stats about the walls.  Press the arrow keys to cycle
 through all the walls. And, one last thing, if you want to end Wolf.
 really cool, press TAB P for pause then press enter.  On you status
 bar at the bottom of the screen, it looks like there was a meltdown!