Big guns.
As a guy who has not broke the twenty inch cold measurement I can say the arms are a real issue for me.
I do believe in training all the bodyparts seriously, and prioritizing weakspots, but poor proportion IS really common in the gym. I admit that I dont train my traps directly very often because on me, the hieght of my traps makes my shoulders look more narrow. I do hit all three heads of my delts though because I am a believer in the wider is better theory on shoulders.
My chest grows easily due to my powerlifting days, so back proportion is my emphasis, but the bird chested; big wing look is just not right. All in all I think alot of people are t-shirt bodybuilders, and maybe only ten percent of the training population are after the total package of symetry, proportion, strength, size, definition, endurance, and flexability.
But thats what seperates the winner from the also-rans so to each their own.
KATANA.