In the newest trialer the guns i have noticed are:
Barret REC7
UMP
Glock 17
MP5 with no stock
a Shotgun (Looks pump action maybe a Benelli M3?)
M16 with M203 Grenade launcher.
And guns from the first trailer if you dont no;
Steyr Aug,
Ak-103,
Unknown Sniper Rifle,
FAMAS,
SVD Dragunov
Heres the link for the Trailer in slow motion
[ame="
https://www.youtube.com/watch?v=cWAn6HWJ4Q4"]YouTube - Modern Warfare Teaser #2 Slowed Down HD[/ame]