Of the guns I have now ....it would be a Browning Citori O/U - the XS Skeet model, adjustable comb, in a 12ga with 30" barrels....( and I could download it like a 20ga ..) or up to a 12ga. I can hunt upland birds with it / even waterfowl ...and shoot all the clay target games with it -even though its not optimal for Trap.
If I was 30 yrs old ( or 30 yrs younger)...and serious about competition ...it would be a Krieghoff K80 - Trap stock with parallel comb, adjustable comb,
30" barrels, with a full Carrier Barrel and a full set of tubes for 20ga, 28ga and .410 from Briley.