Uninvited guests is like an ENM but not quite the same procedure its in monarch linn and it is a quest, nin/dnc can kill or any good melee, i have did it on war/sam and you just throw everything at it in your 30 seconds or die, has quite weak hp id say about 4-5k but it does hit back hard so you need to drop it quick in that strat.
Other one i can think of is Holy Cow in Bearclaw pinacle, its a buffalo NM that hits for something silly like 1k dmg normal melee attacks but nin and thf can solo it but it will be a big challenge for most people.