Gohan trained with the Z Sword but he never really used it. It just seems wrong to have Mystic Gohan fighting with a sword, and I wouldn't be comfortable with it... the only viable sword character, other than Trunks, would be Dabura.
Gohan was at his best fighting against Super Buu unarmed. I think that's what I'd like to see in the game - his incredible martial arts skills, rather than him swinging around a weapon.