What puzzle gave you the most trouble in Portal 2?

I got stuck in one of the white paint puzzles for a ridiculous amount of time. Now I want to play through the game again =p

Anything by Mevious.
In the mainstory, the part of the game where Cave talks about the lemons (White paint puzzle)

Alright, sorry for this bump, but I would love to know some more people's trouble in this game :P

I got stuck at the puzzle where Atlas and/or P-Body make a cameo. I spent about an hour trying to momentum-portal myself to the platform the first cube was on. XD

When Glad0s "rebuilds" the facility and you are dumped into pristine room with a laser puzzle. I overthought that one really really hard. Not at all complicated, but for whatever reason it eluded me for a few days.

Anyone else?

Starting the game. I'm pretty paranoid. I always think that Glad0s will appear just as Slenderman did :c

The first time i played. I got stuck when you are entering to the old Aperture..
Any of you remember that part when you are in an elevator and Cave is talking about the Mantis Men? Well.. There... I spent at least 1 or 2 hours trying to know what to do...

I had to search online to find the answer for the one where you had to dump the gel on the turrets, I felt like such an idiot when I realised you could do that.

I hate the color jellies!

Finding a friend to do the co-op puzzles with.

In the main story, I ended up having to google one of them; the one with the first 'refurbished' test chamber where there's lasers and laser cubes and all the laser recepticle things are by the exit door in the other part of the room, that one I just couldn't work out for the life of me.

I also had trouble with the one near the end with the excursion funnels, the gel and the turrets behind a glass wall and the exit door across a chasm behind the turrets. I worked it out in the end without outside help, but it took me ages.

I got stuck on this one. Spoiler if you haven't done it. Clicky

I just never realise the possibility of using the light bridge to stop those cubes going in the water. Seems so obvious now. I refused to look at any solution guides during the game, so this puzzle actually caused me to have a break from the game for a while. Luckily I figured it out when I went back to it.

I don't have Portal 2, you insensitive clod.

First time I played the game: there was some puzzle where you had to drop some repulsion gel on a few turrets behind a glass wall. Took me a while to figure that out.

Community chambers: I haven't played many of them,but when they added workshop for Portal 2. Most of Mevious maps were tough.

The one when we get the white gel.. It felt like we were given too much freedom and the devs struggled with that.

The first one Wheatley made... Thank god he helped me out ;) (seriously though: a lot the puzzles with white gel)

Me and my girlfriend were stuck in the part when we had to collide each other, but after a while we figured it out :3

90% of the puzzles are incredibly difficult for me.

Some puzzles with gels in underground apeture.

A few of the co-op ones were the hardest for me. IIRC, most of the single player ones were pretty easy.

Getting the lowest possible amount of portals in challenge mode.

I think it would be one of the last puzzles in the Single Player campaign, made by Wheatley. It had blue gel, light bridges, turrets and gaping holes. Wheatley said he had a surprise in that too I think, and he laughed like a maniac.

Hopefully now that I've played Portal 2, when I get the chance to play the original Portal, it's easier...

Anybody else?