The top weirdest anime I've ever seen would have to be Serial Experiments: Lain & Elfen Lied. In one you get metaphysical weird and the other you get just off-the-wall crazy weird (respectively). Adding to this is probably the fact that I've only seen the first two DVDs of Lain & the first 9 or 10 eps of Elfen Lied...so I basically know next to nothing of what's happening in Lain...though I get the feeling that even if I had seen them all I probably still wouldn't...>_>