+1 .. came here to say exactly this. While this site is great for finding out what others weapons exist, I don't think any weapons outside of m4, ak, awp are actually used.
well, SMGs are very used today in the competitive scene. 2nd round winning side is usually the time to buy those SMGs, the opponent will probably have an eco round and the added kill bonus given by those weapons are very useful to build up the team economy.
Also the autoshotgun has some use, usually CT side in maps like Nuke (A site) where there are choke points and a CT can spam the weapon against a T rushing inside the bomb site