If you are willing to pay for a high quality holster, I believe you could carry a 155mm howitzer.
I carry a 1911 concealed every day, and I am an average size (5'8"). I carry constantly and comfortably and well concealed under casual clothing. If I were wearing a coat, I think I could carry three of four of them, if I felt the need.
"It is better to be too skeptical then too credulous"
I'm looking at the M&P shield 9mm - it seems too big to carry. I don't want it sitting on my hip...concealed is the keyword. What do you guys think?
Admittedly I'm a big guy but I can carry a full size Glock 17 IWB with no real problem so I don't see how the Shield is too big. A good quality holster and belt are the key.
If you are looking at it for pocket carry its probably on the large size for that but the same can be said for the Ruger or Kahr single stack subcompacts. It's the trade off for carrying the 9mm. If you want a smaller, more comfortable pocket gun you need to drop to a .380 or even a .32 - .25 cal mouse gun.
The question is extremely relative to your own physical size in height or weight, and based upon your apparel requirements from either the weather conditions or the social situation at hand (like during winter with a coat or at a formal party with a suit).
I'm pretty slim and 6ft tall. I don't wear really baggy clothes and so it would need to be one that would stay fairly hidden with any outfit.