The most common things to come up that aren’t reviewable are penalties. Only these are reviewable (including when not called on the field):
-Targeting -Blocking by the kicking team before its players are eligible to touch the ball on an onside kick -A player going beyond the neutral zone while kicking the ball -The number of players a team has on the field -A player making a forward pass or forward handoff when past the line of scrimmage or after a turnover (or a forward pass that becomes legal after another pass is ruled to be a lateral) -Illegal touching of a forward pass or a kick