I've had a couple, both times playing CTF using the following set-up....
Perk 1 - Sleight of hand
Perk 2 - Hardline
Perk 3 - Dead silence
Specialist kill streaks
2 kills (activates after 1 due to Hardline) - Quickdraw
4 kills - Assassin
6 kills - Scavanger
Primary: super soaker (PP90M1), attachments, silencer + extended mags
Secondary: akimbo FMG9s.
The most recent one is going on my You Tube channel in the morning (Youtube.com/SmarterGroup) with some commentary
Yes, I have twice. Specialist package is the way to go in combo with one of the better silenced guns or the T95 in a game mode like dom since it generally goes on longer than tdm or KC. Demo is good for it too.
Came close to it again, against these christmas low levels a lot recently, in one game I had like 6 final stand assist 1 off a moab, Yeajh for final last. Karma for using it too I guess.
I never seen one in a match yet either, i am midway through 4 prestige so had a fair amount of game time.
A friend of mine plays on xbox and he has had around 20 MOABs, without cheating.
He is about as good as me and my best killstreak is 18 ( although i never set out to get them ).
From what i hear from xbox users i know it seems a whole lot easier on that platform
Tis the season to get moabs though with all these low leves, I came close to them not even trying, if you're not getting them now with the specialist package, chances are you never will. Though you still need a lot of luck.
I was only in one game with another moab (did join a few games that already had them), was recently against christmas low level splitscreeners, I still topped the lobby despite his moab, tis the season to get them really.
I haven't got a MOAB as of yet but I have been close on multiple occasions.
When I'm nearing a MOAB, I either die by a payback spawn or some deathstreak that involves dying by someone falling in final stand with a Striker or killed by Dead Man's Nuke.
MOAB's come easy if you're against terrible or new players but I tend to find myself against average to experienced players more often.