Ive come across whole signs being held up with silicon alone as the mounting screws have rusted right out.

Some more tips for you...

A thin smear of silicon over a playfield overlay will make it last forever.

Seals backglasses like nothing else.

Small blob on chimes acts as a volume control

   Classic stuff  

I'm yet to come across a game with silicone/caulking compound holding it together but i've heard of it being done a few times  

I've seen coils held into broken brackets with insulating tape or duct tape though.. my Pinball Pool had this done to it  
Maybe I should keep some silicone in MY toolbox for when i go to do pin repairs