Well, to further the epitome of the M16, I suggest finding the longest silencer you can, a bipod, a huge carrying-handle mounted scope and fitting it all on. I'm sure you'll turn heads, and like somebody else said, it won't be at all normal =P
I agree that M4's are all too common, but instead I would refine this statement and say, poorly fitted and modded M4's are all too common. I was at an airsoft "convention" or event if you will not too long ago where there were TONS of M4's... but, alas, amidst all of these M4's ONE stood out and drew my attention, purely because it was realistically fitted.
lol After saying all that, you could go the opposite way, like I suggested, which is equally just as stunning =P