It has to be my Empire Strikes Back. It's my first and favorite and started the ball rolling (groan) on a really great hobby. I remember getting the Trading Post early on a Thursday morning I left work and drove from Campbelltown to Southwest Rocks to view it. I couldn't say no, it was Star Wars and only $200 even if it did weigh half a ton. Little did I realise it would take over 15 years to get it working correctly but it's still my favorite.
