Cleffa, especially, feels like a surprise standout
#2 INSANITY
Prior to that we also went over Torbran, Thane of Red Fell, Yorvo, Lord of Garenbrig, Ayara, First of Locthwain, Linden, Steadfast Queen, Emry, Lurker of the Loch, and a smattering of others (including the Brawl commanders and Kenrith, the Returned King)
While you can do it two turns after making Karn the fact that Karn is himself a seven mana card rather detracts from any notion of speed you might have for this ulti
Alexi, Zephyr Mage (Masques/Nemesis/Prophecy) Here's the difference between Odyssey Block and Masques Block: There weren't a lot of spells that could kill a three toughness creature in Masques Block, where there are quite a few in Odyssey Block