Demon of the Well
My vote for next month's WAD is, categorically, for Hellbound.
Map 20 -- Traps - 103% Kills / 100% Secrets
Ah, I think this is one of the most memorable maps in KS. Like map 14, it's big and open and positively drowning in both poisonous ooze and fresh air. Depicted is a part of a large tunnel system running through some foothills of bleached white stone, but there's ooze positively everywhere (some of it actually damages this time, although for some reason most of it doesn't). The little bits of scenery visible in the distance and the occasional piece of human artifice at various points suggest the slime-drenched condition of the area is not its natural state, almost as if there's a little mountain town now submerged somewhere down in all that green. Apart from quirky little 'realistic' constructions like the crane with the little cage at the end of its arm, the structure of things here is typically on a grand scale characterized by simple, 'clean' detailing (typically just bends and bumps in the natural terrain), which works well with the green/white color scheme.
Naturally, it's not called "Traps" for nothing. The most recurring snare is a malicious group of phantom barrels that tends to suddenly materialize from the aether around some choice armaments and other good stuff, only to promptly erupt in a lethal explosion (I like to imagine, since this is KS and KS is a little bit bonkers, that these are sentient barrel-spirits on a quest for vengeance against the marine in the name of all of their brethren he has destroyed over the years). There are also some sneaky monster teleportations and things of that nature, particularly involving cyberdemons that like to teleport in behind you at various points in order to keep you pushing onward into new dangers. Of course, since I've played before I was able to deftly evade most of these traps, but I actually wussed out and used a savegame right before going for the yellow key, since that particular trap sort of leaves the realm of 'tricky' and enters that of 'metagamey.'
The highlight battle is, of course, the giant red skull clusterfuck. While most of the actual hitting power comes from the hordes that pour down from the upper level, it's actually the irregular pulses of imps (so MANY imps!) and pain elementals that leverage the real pressure on you, since it's easy to ignore one prong and end up undone by the other. I quite like this setup, actually....I think it cleverly allows for a particularly large range of approaches, ranging from cowardly-but-smart to 'suicidal bravado.' What I did was kill the arch-viles in the key/switch alcove, take the secret invulnerability artifact (readily visible earlier in the level if you keenly survey your surroundings), and then use it + BFG to decimate the vile/noble/revenant jamboree on the upper level, using the many available rockets to beat back the cloud of PEs afterwards. Running into the imp tunnel at the outset like Cannonball described sounds interesting, too, I reckon I'll try that next time I play.
With the brief exception of the yellow key bullshit, I like this map. Gusta seems to like to do more hemmed-in smallscale stuff a lot (see, for instance, the very next map), but I think he does quite well with big open spaces like the ones seen here.