These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The Protozoid Slimers, which hatch from eggs, hide in vents, and climb up on your screen, tearing you apart unless you kick 'em quickly. They're pretty hard to hit in the open, too. Luckily one hit of anything kills them if you can connect, including the otherwise damage-less Shrinker.
Similarly, the kamikaze drones are equally as annoying and probably more dangerous.
Literally appear in Lame Duke (at least episode 2 level 1), as this beta version features a bat enemy which was dropped from the final game.
In v1.3D, you could select the Mighty Foot as a weapon and then kick with the melee button, at the same time! Result: Duke somehow manages to run around while both of his feet are on screen, whacking enemies. (Un)fortunately fixed in later versions.
The Build engine is notorious for its flaws that allows mapmakers to come up with interesting map ideas. Bizarre takes this fact and drives it straight into Mind Screw territory.
There is the possibility that you can die as you're exiting the level. If that happens, you start the next level with your stuff intact and 100 health.
Moment Of Awesome: At the end of episode 2, before fighting the boss, Duke states that he'll rip off his head and shit down his neck. Cut to the post-boss battle cutscene where Duke follows through on the promise.
Porting Disaster: The Tiger Game.com version. In fairness, it was actually one of the most advanced handheld games of The Nineties; there was just no way to replicate the Duke Nukem 3D experience on hardware barely equivalent to a Game Boy.
Less so the Mega Drive port. It does have a pretty decent framerate, considering how big the "first-person view" screen is, compared to other FPS games on that console, not to mention the save system which allows you to backup everywhere. Nothing else makes up for it properly, though: the whole port consists of 9 new levels, very loosely based off the Lunar Apocalypse episode, all done in a Wolf3D-like perspective, all peppered-up with barely audiable music and slightly messy controls. * And that's not even for Duke himself: in order to pause the game, you will need to not just press the Start button, but also X, Y and Z, all at the same time! Oh, and it didn't help that shortly after the game was released in Brazil (the only country that received a Mega Drive port), the whole thing got banned.
Episode 1, level 3 features a ridiculously-tricky segment where you have to jump and duck past a bunch of infrared laser sensors. If you hit one of the lasers, bombs go off and kill you instantly. Not to mention that some pig cops are on their way to kill you as well. And if THEY hit the lasers, it also triggers the explosions.