Call button use I remember:
1. The drunk guy next to me spilled his entire bloody mary into my crotch.
2. The person next to me passed out.
3. Total lack of attention from FAs, in my experience CO was famous for leaving your meal tray in front of you for hours on INTL flights.
4. Not UA, but on one occasion when the oxygen marks over my seat fell down for no apparent reason. (The FA just tucked them back in and closed the cover.)
5. In INTL business when my seat completely failed to operate.