What are the fastest possible games in which only all pieces and all pawns are captured? I did some searching myself.
Pieces Only
[Title "me, chess.stackexchange.com 3/2/2019, Non-Unique Proof Game In 13.5 Moves"]
[FEN ""]
1. e4 e5 2. d3 d5 3. Qg4 Qg5 4. Qxc8+ Ke7 5. Qxb8 Qxc1+ 6. Ke2 Qxb1 7. Qxa8 Qxa1 8. Qxf8+ Kd7 9. Qxg8 Qxf1+ 10. Kd2 Qxg1 11. Qxh8 Qxh1 12. Qe8+ Kxe8 13. d4 Qe1+ 14. Kxe1
Pawns Only
[Title "me, chess.stackexchange.com 3/2/2019, Non-Unique Proof Game In 16.0 Moves"]
[FEN ""]
1. e4 e5 2. f4 f5 3. g4 g5 4. h4 h5 5. d4 d5 6. c4 c5 7. b4 b5 8. a4 a5 9. bxa5 bxa4 10. cxd5 cxd4 11. exf5 exf4 12. gxh5 gxh4 13. Rxh4 Rxh5 14. Rxa4 Rxa5 15. Rxd4 Rxd5 16. Rhxf4 Rhxf5