I have a lot, tell me if I am missing any.

Canon:
Felix x Harmony

Kobaltic x Anna

Ares x Kira

Frighten x Arron

Thunder x Issac (TKDitto613 HOPEFULLY!!)

Non-canon (ones I will write fanfics about but IDK if I will ever publish them to Wattpad. Don't judge me for these):

Harmony x  Clockwork (YAS)

Harmony x Bella (YAAASSS..)

Anna x Cassandra

Kira x Zeto (PocketDoodlez)

McKenzie x Knife (Joking, it's like AntiSepticEye x Knife)