Least favorite tile/element/monster?

[rockdet]

...I actually did break a flatscreen monitor by punching it, but my fist didn't go through it. The punch just created a web-like effect that slowly overtook the entire screen, turning it a permanent black...

Now that's scary

And my least favorite thing will probably be the teleporter. Despite its incredibly huge potential for anything, people have reversed its original uses to trick players and create artificially hard puzzles, just by the sole fact that you don't have a single clue what you have to do until you've tried everything at hand, to realize there's a second degree partial post involved which tells you not to pick "that one key you're sure you had to take" (cue LUNiT).

I also don't like anymore the fact that you have for the most part absolutely no idea what's on the other side and you must be prepared to react to evilness (cue Telenet, Drawn and Quartered, Oversea Delivery, Alphabet Soup, Tele-Rooms, etc.)

Of course it has incredibly huge potential like I said. I just feel it has turned as a mean for difficulty more as a useful pleasant tile that gets you somewhere else like it was originally meant to be.

Also, I hate the invisible walls too, but there has proven to be interesting things (fair too) to do with them.

Walkers are not in that list and will never be for me. Blobs as well.