Could work with dialogue, or by themselves. Here were a few I thought of:
-Thumb’s up/thumb’s down
-“Loser” L on forehead
-“Whatever” W (which I remember seeing in It Starts With a Bra.)
-Cracking knuckles
-Punching own other hand
-“What the heck?” turning palm to ceiling
-“Talk to the hand”
-Finger guns (pretty sure this has been suggested already)
-Jazz hands
Of course, this is not necessarily a complete list!
gesture