Khadgar’s ‘Time for a lesson, insolent pup!’ 
— especially when played next to Arfus in Mercenaries. 
https://hearthstone.fandom.com/wiki/Mercenaries/Khadgar/Miscellaneous
(Yeah, I know, many Mercs lines are taken from cards, but whatever…)
Nemsy’s lines in Mercs…
Cookie — his ‘La-la, barloopah eh!’ (also an apt and light-hearted response to Kurtrus’s ‘UNRELENTING FURY!’, by the way ) and especially ‘mocking mrgl sounds’ (from BoM, I think):
https://hearthstone.fandom.com/wiki/Mercenaries/Cookie,_the_Cook#Tasks
Chieftain Scarvash’s ‘Trogg no stupid! Trogg make you stupid!’ — resonates with many reactions that I see on this forum.
And so on, and so on.
As for negative ones, I used to almost get the impression the Amani Berserker is trolling me: ‘Heh-heh-heh, it’s time for a little blod!’ (sic) or something like it…
Some of these ones would qualify, especially the likes of ‘Papeepooyah!’ and ‘Eeeyah call that a weapon, ha?’
But these are just some quick examples, there are probably many, many of them…
PS Anything by Tamsin Roame is an auto-squelch from me.