I just hope it's not the lootboxes again (like when there's a random thing in it) because after vowing I'd never buy them again, I'd eventually break once again after seeing people got something good in those, buy a couple myself, and get some crap I'm not interested in.

THIS. I have always wanted the full version.

I'd love to buy:

Costume Quest 2

The Lost Crown

The Last Crown: Midnight Horror

You probably jest, but I found that game genuinely a little tense and chilling when I played the shareware episode in the mid-'90s. The way a skull gradually superimposed itself over the portrait of Hugo in the corner of the HUD as you took damage actually creeped me out a bit. Plus it was actually difficult (though whether it was "good difficulty" or "bad difficulty", I couldn't now say).
Of course, like most old Wolf3D clones, I probably couldn't stand to play it these days.

I'm almost certain the Halloween sale will follow the format I hate the most, from all that GOG has tried out. It will probably a "treats" sale. Pay $2.99 and get a treat that contains a unknown game. This means that some rare games will end up being ridiculously cheap, some will end up at previous historic low, and some will have been cheaper before.

As far as I'm concerned, the problem with such a Halloween sale is that, spooky/horror games aren't really my type of games, and I just can't see myself paying to get a random game from I genre I don't play.

I'd expect the sale to begin three hours from now, or if later, then seven hours from now. We'll see...

The Sale appeared on homepage for about 15 minutes, but not really functional.
GOG have pulled the banner.
Not sure when will it appear again.

It was the first 3D game I ever played. It didn't scare me or give me chills, but it did make me shit my pants. I'd never seen anything like it before, I was blown away.

The catalog's 'Sale' tab has been renamed to 'Trick or Treat Sale'.