Depends on your budget. If you don't really have one, a Beretta 694 ACS (All Competitions Shotgun) would be a nice choice, especially if you would want to shoot trap are any of the other disciplines but it would set you back about $6500 new. Could probably find one cheaper used but won't be cheap. If you don't want to got that expensive, then a Browning 725 Sporting, Beretta Silver Pigeon, Winchester 101, even CZ makes some decent over/unders and any of these would do the trick. Get one with choke tubes. The chokes you choose could be very dependent on the course you are shooting.