Looking for parts:
SS BB Starscream - left (his left) null ray cannon.
2007 Night Watch Optimus Prime shoulder pads and detachable flip out ion cannon
“The world seems to work in predictable ways, and you think you see the pattern. But that's fatal. Because it's only a pattern until you meet the first event that doesn't fit. And by then it's too late. By then, all the tricks you've learned to deal with the world -- well, they just don't work anymore.” - Neverwhere, Neil Gaiman