My favourite Arnie line doesn't actually exist, but was invented by a friend of mine for the film Total Recall. As I remember, a baddie is hanging off an open lift, whereupon they pass some great concrete girder or something, which chops his arms off. Arnie then has some very lame line like "enjoy the party", as he throws the arms back down to the baddie. My friend immediately shouted out a line so great it would have been Arnie's most quoted - as he throws back the arms, he says
"Catch".