Kit Unlocks
Using a kit as you play will level it up, just like your rank. Level up your kit to unlock more kit exclusive weapons or gadgets. Battlefield 3 calls it a score, such as Assault Score, but it's the same type of XP. The only difference is it's being directed to a Kit.
The following lists show the score you need for each unlock. Some weapons are only unlocked in Co-Op mode with a Co-Op Score (CS).
Assault Kit
0 AS - M16A3 (US) / AK-74M (RU)
4,000 (4,000) AS - Defibrillator
7,000 (11,000) AS - M320
11,000 (22,000) AS - M416
16,000 (38,000) AS - M26 MASS
22,000 (60,000) AS - AEK-971
29,000 (89,000) AS - M16A4
35,000 (124,000) AS - F2000
42,000 (166,000) AS - AN-94
54,000 (220,000) AS - M16A3 (RU) / AK-74M (US)
17,000 CS - KH2002 (Co-op)
160,000 CS - G3A3 (Co-op)
Engineer Kit
0 ES - M4A1 (US) / AKS-74U (RU)
3,000 (3,000) ES - FIM-92 Stinger and SA-18 IGLA
4,000 (7,000) ES - M15 AT Mine
7,000 (14,000) ES - SCAR-H
11,000 (25,000) ES - EOD Bot
15,000 (40,000) ES - M4
18,000 (58,000) ES - A-91
24,000 (82,000) ES - FGM-148 Javelin
28,000 (110,000) ES - G36C
35,000 (145,000) ES - M4A1 (RU) / AKS-74U (US)
120,000 CS - SG553 (Co-op)
Support Kit
0 SS - M27 IAR (US) / RPK-74M (RU)
4,000 (4,000) SS - C4 Explosives
7,000 (11,000) SS - M249
12,000 (23,000) SS - M18 Claymore
17,000 (40,000) SS - M224 Mortar
20,000 (60,000) SS - PKP Pecheneg
30,000 (90,000) SS - M240B
40,000 (130,000) SS - M60E4
40,000 (170,000) SS - M27 IAR (RU) / RPK-74M (US)
Recon Kit
0 RS - MK11 MOD 0 (US) / SVD (RU)
5,000 (5,000) RS - T-UGS
8,000 (13,000) RS - SV98
13,000 (26,000) RS - SOFLAM
19,000 (45,000) RS - MAV
26,000 (71,000) RS - SKS
33,000 (104,000) RS - M40A5
42,000 (146,000) RS - M98B
49,000 (195,000) RS - MK11 MOD 0 (RU) / SVD (US)
58,000 CS - M39 EMR (Co-op)
Co-Op Unlocks
63,000 (5,000) CS - MP412 REX
63,000 (17,000) CS - KH2002
63,000 (34,000) CS - MP7
63,000 (58,000) CS - M39 EMR
63,000 (86,000) CS - 93R
63,000 (120,000) CS - SG553
63,000 (160,000) CS - G3A3
IF LIKED MY POST THEN HIT ThANKS AUR THE RePO BUTTON