So after the tournament at WTII games, a few of us were discussing whether a model with gunfighter could trample and then shoot a spray attack. the two models we were talking about were torch and typhon being the only two we could think of that had sprays and rules that might let them use those sprays after a trample.
I went and found the relevant ruling on the PP forums: http://privateerpressforums.com/show...ter%2B+trample
there are a few others out there, this one was just the easiest to read. so it looks like Torch is allowed to trample then buy spray attacks because he has virtuoso. the trample replaces the initial attacks but does not use them, so he can buy up to his ROF (i think it's ROF 1 on his gun).
Typhon on the other hand cannot buy sprays after trampling, because he has gunfighter rather than virtuoso. the linked ruling says that gunfighter does not allow ranged attacks to be made after a trample. Typhon has his own unique ability to divide his initial attacks between ranged and melee attacks, but since the trample is used in place of initials, that wouldn't help him in this case.