It's true all Airbus (A300 & A310 excluded) wing tip strobe lights flash twice per sequence and all the rest once. The thing to watch out for is once the airline engineers get their hands on them this may change, but usually doesnt.
The only other one i know of is a way of differentiating Boeing 737 classics from Next Gen. (400s from 800s mostly). The classics have independent anti-collision lights (they mostly flash at different times), NG aircraft always flash simultaneously.