Jonathan Schrantz explores five of the most popular (and actually playable!) countergambits available in chess:

5. Winawer Countergambit

4. Von Hennig-Schara (Counter)gambit

3. Falkbeer Countergambit

2. Albin Countergambit

1. Blumenfeld Countergambit

https://www.youtube.com/watch?v=-SbR9E_SLMA