I have to echo Robert on this one, unfortunately... My most famous albatrosses are:
1/72 Space Shuttle... awaiting a decision about which mission to model for over 7 years...
1/9 scratch figure of Yoko Tsuno (a famous comic strip character in Belgium)... primed but awaiting painting since '98 ...
1/35 IS-3; the Tamiya kit, with scratchbuilt engine, and all details inside... awaiting painting for the last 4 years
1/100 Boeing 727-100; the old cr.py VEB kit, all opened up and everything down, awaiting I don't know what since '99...