I like to use a Rugby Jersey with Collar for practicing in heavy realistic clothing. How about an Official 10th Planet Barbarian.com Rugby Jersey for those who live in colder climates?
But I would estimate that even in colder climates there is about an equal chance to end up in fight wearing heavy outdoor clothes (Gi) in the winter or just your board shorts (No-Gi) in the Summer.
The plaid Jac-Shirt is the official dinner coat in my town