Nice to see someone's heard of the Amazing Jonathon, he is the anti Blaine, there's two others in a similar vein, The Bastard Son of Tommy Cooper, who's act seems to mainly consist of wearing a fez, doing a bad Paul Daniels impression and doing 'tricks' that involve knives, needles, fire and his own body. I remember seeing him 'live' and he had warnings before he came on that he 'may offend' due to the amount of blood etc involved. Also remember him placing a small nail on his tongue, then forcing it out thru his tear duct. Now that's entertainment. What makes him 'funny' is the fact that's he's doing criminally insane things in nothing but boxers and a fez, with a silly voice, and the whole act in rhyming couplets.
If he sounds a little tame, and you ever get the chance, do see Jerry Sadowitz, he's a legend amongst comics, a talented magician and makes Frankie Boyle look like Joe Pasquale in terms of his level of offense.
Pleased to see a few votes for Charlie Brooker, tho he's no stand up, his books, TV show and newspaper columns are always good, to the point where he can make even the tired old 'bloopers show' entertaining, check this clip from QVC where they're selling TVs and 'screen burn' is on at the time.
http://uk.youtube.com/watch?v=vPKRs3LF88M
I'll add Stewart Lee to the list, as he's little known, apart from the 'Fist of Fun' show in the 90s, but had a large part in writing and producing the 'Jerry Springer Opera' now the most complained about show on British TV, and if not the funniest comic ever, one of the bravest, check out his bits on youtube, in front of a scottish audience, where he pretty much tears apart Scotland, the scottish people and William Wallace, their national hero.
Lastly, not a stand up again, but one of the most important people in comedy of the past 20 years imo, Chris Morris, creator of Brass Eye and the weirdfest that is 'Jam',essentially a sketch show set in Silent Hill, possibly the creepiest and strangest 'comedy' I've ever seen.