#4...I like it, mostly because all I can think of is a revolver with an underslung cleaver. Sort of something I'd expect to see in the new Mad Maxx movie, some marauder waving it around and howling 'Step away from the gasoline!'
I love number 6, looks like something you could happily bludgeon someone with once the ammo's spent. In fact, would you mind it terribly if I turned it into a papercraft piece? I'd give you the file once I'm done, of course, it just looks too good to not have in one's hand.