Agumon (DigiVenture) is a member of the Digimon Trio. He is best friends with Veemon and Guilmon.
Agumon's behavior is not exclusively childish like Fan:Psychemon (DigiVenture), but he clearly does not have a serious demeanour either. He conducts himself rather like a sensible child.
This is Agumon's Digivolution. (All of Agumon's Digivolution Digimon's attacks are on the Digimon's page).
GeoGreymon or Greymon O
Agumon's Champion for is GeoGreymon or Greymon O. He Digivolves to this form mostly when he is facing a Champion-level Digimon. He mostly Digivolves into Greymon O.
Agumon's Hybrid/Ultimate for is BurningGreymon he Digivolves into BurningGreymon when he is facing an Ultimate-level Digimon. The only time he doesn't Digivolve into this form while facing an ultimate Digimon is when someone else is using the B Spirit of Flame.
Agumon's Mega Form is WarGreymon. He Digivolves to this form when he faces a Burst Mode or Mega level Digimon.