Our first experience of TRAINING.bsp was waiting an obnoxiously long time for the map to download.
This wasn't rare, in and of itself, as there wasn't any size limit on a .bsp file and a lot of makers thought that it was the height of comedy to add South Park voice clips to every conceivable player action. I remember wondering if TRAINING would be a voice-acted tutorial for advanced techniques like grenade jumping or building human ladders (one popular trick for finding shortcuts, or just glitching your way out of a map, was to get another player to crouch, stand on their shoulders, and repeat the experience with more and more teammates).
What we got, though, was the clan squeezed into a small, monotextured room with a single dark exit and the simple caption of "TRAINING" on our screens. So far, so unimpressive. The exit took us out into a dimly-lit subway tunnel, which we proceeded along.
If you've figured out the punchline to this one already, you're quicker than all of us.
Either the designer clearly didn't have much of a sense of scale or they'd never seen a proper subway, because the ceiling of the tunnel was way higher than it ought to be, and the tunnel just continued straight without any change in texture. Just as I was starting to wonder whether we'd encountered an unwitting sequel to The Irritation Machine, I suddenly started seeing bullets fly and my health drop. The level had spawned a bunch of grunt enemies, almost on top of us.
They weren't anything special, although the maker had apparently modded them for increased health and damage -- a common cheap shot among co-op map makers to counter the increased firepower that enemies will be facing -- but just as we had finished mopping them up, a message came through on team chat:
Jersey99: OH FUCK
We looked up, and as one saw the bright light coming towards us down the tunnel. There was just enough time to realise we'd been had before a train ploughed through the lot of us with a deafening "WOO WOO" whistling sound effect, instakilling everybody who was still alive and ending the map shortly after.
As I said, we really should have seen that coming.