I'd have to say my Lexus RC-F with the Aventador V12 swap, or my other RC-F with a Viper V10 swap.
(Don't give me any shit about the swap, trust me I know. I don't like the idea of even having any V12 swapped car either, especially in all reality, it wouldn't fit in any of the cars in real life, muscle cars should stay a V8 (V8's sound better anyway).
I agree that the V12 swap is dumb, should never have been implemented in the first place. The only reason I have it is that I wanted to build something stupid.