Good guns: (FR-F2, DSR-1, SA58 PARA require rank of Master Sargeant to purchase [i think])
Out of these, I would pick M4 MK3, Veresk/Galil MAR, and TPG-1/ASW .338, if i was low rank.
MP7 (headshot gun)
Veresk (headshot gun, both MP7 and Veresk have great penetration of armor, veresk has high dmg and recoil [for a submachine gun])
Striker (best shotgun as of right now, use random dmg barrel)
Spas-15(use ROF trigger, not accuracy.)
K1A1 and Galil MAR are good carbines for PM.
Kriss Super V is a good SMG also, make sure to buy the 28 rnd magazine, and
Calico M950 is a decent SMG, like a PP19 with better ROF, but I wouldn't suggest it.
M4A1 MK3 (burst for headshots, low recoil and decent dmg)
SA58 PARA, hard to use, but has high damage/ROF combo, along with high mobility.
FAMAS MK3, tight crosshairs, low rank requirement, low recoil. (pretty much any MK3 weapon is good)
R4 Remington and XM8 are pretty good/easy to use also.
SR25 is the best Euro semi-auto sniper, 93 dmg w/ reinforced barrel, and a 20 round mag with quick reload. Can one shot kill often.
FR F2, TPG1, PGM .338, ASW .338 are good, reliable one hit kill snipers.
WA2000 is also a good sniper with highest dmg of all semi-autos but it should be used like a bolt action, because its magazine only holds 6 rounds.
DSR-1 is a great gun in CQC because of the short time to quickswitch, but it has a high rank requirement.
Beretta 92F is best Euro pistol.
MK23 is pretty good too with 40 dmg, and
CZ75 is a good spamming pistol.
Glock is a cheap pistol that does almost as well as Beretta.
That's my list.