Some things that turn an otherwise platonic, innocent situation into an air-crackling, whimpering-like-a-dog torture fest:
-That crunch/scrunch sound of leather as they move slowly and readjust themselves
-Catching a glimpse of their leather boots and shoes
-Languid movements and body language
-That amused look that says, "yes, I know you want me. Now what are you going to do about it?" ... usually followed by a slightly raised brow
-Alternatively, a bashful, blushing butch! Makes my mind go to very naughty places...
-Aviator sunglasses or an otherwise flattering pair of shades. There's something about not being able to see their eyes fully which adds an air of mystery.
-A slightly popped collar on a peacoat in winter paired with an understated, classy scarf... though a well dressed butch in general makes me conflicted - I don't know which I'd enjoy more: watching them move with those clothes on or ripping them off... Decisions, decisions...
-Running fingers through their hair (their own fingers or mine)
-Watching their hands when they drive... I find it hard to keep my hands to myself after that. That's all I need for foreplay!
-Kiss on the back of my hand, a tongue on the palm, etc...
-Tall, tall butches... I'm 5'8 and if you're taller than me, butch, and breathing, I'm basically going to try to rip your clothes off later. No exceptions (well, unless someone else got to you first!).
Basically, I'm a horny bastard.