MP-10 Hasbro version. The definitive G1 Optimus, hands down. Didn't realize I still have such strong emotional ties to the G1 era until I got him(The childhood memory value of G1 figures quickly faded away not long after I started collecting re-issues in the early 2000s. Modern toy engineerng is the main thing that keeps me collecting nowadays) And this figure got me back into collecting Masterpiece.

MP-09 TakTom verson would come close in the 2nd place. Has minor design flaws and is uber finicking to transform but the end results in all four modes are quite impressive. I think it's Hironori Kobayashi's finest work in the MP line.

I have yet to get the Hasbro soundwave but he should be in top 3 just for the money value.

P.S. I loved Hironori Kobayashi's creativity but gotta now Shogo Hasui's Masterpiece figures have won me over. He's an absolutely brilliant designer.