PM-9.  I normally don't play search but decided to get some of the titles and was using my PM-9.  Got a few final kills and people were ooohing and aaahing about these guys getting killed by it.  Apparently it doesn't get much love.

It reminds me of my uzi days in COD4 and MW2.

PP90M1 with Rapid Fire and Extended Mags, absolutely amazing and unbeatable by any gun in CQC. I drop akimbo FMG9 and Striker users in CQC with that gun 9 times out of 10, its an absolute beast.

If you're looking for an SMG to use on a larger map, MP7 + Range is the way to go. Its basically an AR with SMG mobility

The P90 is also my favorite. The iron sights are good enough that you can try out all of the proficiencies and attachments on their own to get a good feel for the best combination. I like to switch between Range with Silencer and Kick/Focus with Rapid Fire. With the UMP and the PP90, I always feel like I have to run the red dot sight to maintain my accuracy. With the P90, I'm just as accurate hip-firing as I am ADS. And the magazine is big enough that I can take down two or three targets before I have to reload.

Mp5, no one uses it, gun itself is not that bad, comperable to the UMP.

UMP45 w Rapid Fire and Range. MP7 w Rapid Fire and Range.

Both awesome to run and gun with. MP7 has a little better mobility.

My Favourite SMG would have to be P90

Its good in any situation and has a hell of a lot of accuracy with staedy aim hipfire

I also like UMP45 & MP7

The UMP works great for me

I like the MP7 and PP90M1, but I just seem to do better with the UMP. Once you learn to manage the recoil it's pretty unbeatable

PP90a1 - attachment - rapid fire - silencer

MP7 - attachment - rapid fire - silencer

well personally. my rank for these smg's are

1- Mp7 silencer rapid fire (i know its only 11% increase but it helps alot)

2- Pp90m1 rapid fire extended mags

3- P90 silencer range

4- UMP rapid fire kick (used until level 30 then i stopped)

5- mp5 (havent use)

6-pm9 (havent use)

Its far from the best but my favourite is prob the mp5, with rapid and silencer. Everyone hates it and for that reason alone i love it. prev cods its been a beast but mw3 has dulled it right down although i have still been one off a moab with it so it cant be that bad. I also have it at level 31 and it didnt take long at all.

P90 hands down.  Great clip size, fire rate, equip Steady Aim and you can easily get hip fire kills. I always run it with RF and Silencer or RDS. 

I also love the PP90M1, MP-7, and UMP45 but the P90 still out beasts them all. 

UMP + silencer + kick