Animutations (hyakuugorichi-whatever and so forth) were great in the early aughts.
I consider "under construction" gifs a predecessor to modern memes, what with their progression to include Simpsons characters and other stuff like that.
Some comic strip reconstructions, like "garfield minus garfield" and "dilby" are brilliant.
Zombo.com is equally so in its simplicity.
Zalgo bores me. So does rage face and rage comics. I think the internet is overpopulated now. It doesn't feel secret or special when you find these things any more, because everybody knows about them. I like the whole aspect of culture jamming and repurposing and making it really funny or really weird. Zalgo should be good but I think whoever makes them is just trying too hard conceptually speaking and not enough effort in execution. Or that it's the same joke every time without enough variety to be interesting.
thecrow174
I kind of like this one.

The demotivational poster one or the Picard facepalm?