I can't pick one so here are some of my favorites:
Chen-EXO Promise 2014 and Hey Mama and so many others like damn this dude can just hit it
Kihyun-Lost in The Dream
Haechan-Go
Wendy-Happiness (the whole 'Shine on me part' is basically a whole high note)
Hongki-Wind
Taeyeon-I
Taeil-Simon Says