Achtung achtung, reactor meltdown imminent. Please evacuate the premises...
Achtung... Learning Channel by Richard Peck is an 8-level scenario for the Third Encounter. As you may already know, Richard Peck or RDP is a major name in the Mac modding scene. Having made dozens of scenarios (some of them probably unreleased), his sheer mapping body count goes into the hundreds, only matched by the likes of Thomas Weiling. His maps are rife with interesting combat scenarios and creative designs, though there's also a fair share of your basic square rooms and tight passages. Difficulty level is generally high, involving many enemies and obligatory secret pushwalls.
Achtung Hund (Faces) by ToddAM [?] is a 3-floor scenario for the First Encounter. I have no idea what is the word "Faces" meant to indicate. The maps are very extensive, spanning pretty much the entire mapping grid, and are populated by a reasonable number of enemies. Todd was able to produce decently creative output within the usual First Encounter limitations.
Actung Shabbs by Andres Vialpando is a 3-level Third Encounter scenario. You're going to hear about Andres again soon - a lot. In the meantime, have this small scenario as a sampler. The maps are very small, but relatively interesting, with designs progressing beyond simple square rooms. The going is tough, for example in map 2 you will have to make do with just one medkit while facing a large number of enemies on such a small map.
Of course it wouldn't be a MacenWolf mapset post without an unknown author somewhere in the mix. Achtung Zwei offers three levels for the First Encounter. The most interesting aspect of these maps is probably the death traps, meaning rooms filled with boss enemies whom you're obviously not meant to fight. Have fun running away from them, that is if you don't die instantly.