Favorite: Nami's Laugh https://i.gyazo.com/ecb3d2f46325216d02624bb6cb84d028.gif Runner up: Leona's Dance https://i.gyazo.com/afd92ecb4ca409d727c4fd2493728142.gif
How about emote spams you hate? I couldn't think of any I particularly hate; I only dislike when they're used to BM, and I just mute them at that point.
Darius laugh spam.
laugh spam
and
dance spam.. holy fuck how does someone twist his arm so fast
lissandra lol I I I I I I I I I I SSSSSSSSSSUUUSUUSUSUSUSUSUSUUSSSSSSSURRENDER CLOCLOCLOCLOCLOCLOCLO and heimerdinger DOODODODODODODODODOODOOSODODODOODODNT WORDODODDODODODDOODDODODODODODO
Donger Laugh Spam. 
Hahahah Yeaaaaaaaaah 
Bot Nunu Laugh is FUCKING EVIL
Nasus Yoyoyoyoyoyoyouryouyoyoyoyoyoyouryouryoyour legacy... Therthertherthertherthertherthere is such potential in one mortal life... Also his dance kick spam
Runner up Vel'Koz laugh/dance combo spam (his tentacles go crazy)
Rek' sai taunt spam
oooooh my, how it destroys ears :D
Final Boss Veigar Dance/laugh.
I would type bot nunu laugh but I find singed's laugh to be the most blood boiling, it makes you want to chase him so hard (story of my laning phase against him). Also sejuani's dance spam looks incredibly suggesting when another champion is right behind you (try it).
BC Prime Cho'gath dance.
taunt.
Su-su-su-su-su-su-surrender! My triumph is inevitable!
Oh Darn!
