I see people complain about every weapon. I think they do it because they are mad they are getting owned, and/or they have no skill in those weapons and are jealous. I personally don't think any weapons are noob weapons. Like I said in a post before, every weapon takes some kind of skill to use. For example, if you like to sit back and snipe every game, You probably wont be too good with a UMP or a shotty. on the flip side, if you use close quarter weapons (shotty, UMP) chances are you cant snipe worth a poop.
Whenever someone calls me a 'shotty noob' or a 'nade noob', you just have to tell them 'the end justifies the means' (it doesn't matter how you get the kill as long as you get it). That usually gets them to shut up.