I forgot about one in an R22 - as a student pilot on a night cross country flight with a CFI, had a fuel leak at the carb (mechanic screw-up, didn't tighten a fuel line).
Started the flight with full fuel, we both noted the fuel gauge was dropping a bit faster than expected as time went by, but then again those gauges aren't the largest or most accurate in the world to begin with either. We cut the flight a bit short as that continued & headed home just in case, on short final the low fuel light came on.