Alright, that Kulle-Aid potion was pretty sweet, the rest are pretty much standard fair in terms of stuff to look for.
Personally my favorite legendary is this [http://us.battle.net/d3/en/item/nagelring] nifty little ring. Found this thing at lvl 23 with one of my more recent characters and I wore it the entire game because it's passive is hilariously overpowered.
Long story short: upon equipping the ring, you summon a fat little bastard that runs around with you - up to 4 can be with you at any time - and they run out and kamikaze your enemies for AoE damage. Like...hilarious amounts of AoE damage. Like...when I went to fight the Butcher, he was dead the moment his little stomp-in cutscene was over...and I still had 2 little bastards left over. Their explosions are simply too powerful to pass up, so long after I had found rings with much...MUCH better stats, I kept the Nagelring because those crazy little bastards were just way too powerful. I don't know what they're scaling off of, but they're by far the most powerful "weapon" that I've ever found in the game. :3