A coach's request to have a specific call, such as a goal after possible offside or goalie interference, checked on video. Only some leagues allow it, under their own rules.
The referee raising an arm straight up without blowing the whistle, to show a penalty will be called once the offending team gains control of the puck.
The linesperson's signal for icing, usually an arm raised while icing is possible and then arms folded across the chest once it is called. How icing is judged depends on the rulebook.
An official who mainly calls offside and icing, drops the puck for most faceoffs and breaks up scrums. In many systems they can also report certain penalties.
Standard hand and arm motions officials use to show calls to players, benches and fans. The exact motions are set by each rulebook or officiating manual.