I believe I'm level 19 now in the beta, and have found some guns I find to be my favorite already:
-Remington 870 (shotgun). I find this thing to be by far and away one of the top 3 guns, at least for this map. With ext. mags (7), it is a piece of cake to take down an entire squad in seconds and keep on going. One shot kills like crazy.
Those 4 are a clear step above the rest, at least to me. SCAR is a monster at pretty much any range, the 74u was my favorite in BC2 and it's awesome in this game. UMP might need to be nerfed, IMO. I win pretty much every gun fight with that thing.
How bout you guys?