K3K33-SFH5X-WBX5B-BJB33-Z9J3F - Halloween skins
5JWT3-3H5FB-SCBX5-TJ3JB-H5R6X - Luck of the Zaford Skins & Chulainn SMG
WTCBJ-FTCXF-5TXCT-3TJ33-TZXW6 - Krieg's Loverpalooza Skin
KBWJJ-WTXB9-C59J6-WFBTJ-TK6BJ - Humor in BL2? (GDC - http://videogamesuncovered.com/news/want-a-free-gun-for-borderlands-2.html)

CTKTJ-JSWJF-SCJXK-3TJJ3-RWTKX - The Pre Sequel Heads and Skins (Krieg as Scav)
53WT3-59KJX-95B65-3J333-S9JW9 - The Pre Sequel Heads and Skins (Gaige as Moon Moxxi)
W3C33-H653X-9CTR5-3TBJ3-HZ99S - The Pre Sequel Heads and Skins (Zer0 as Claptrap)
KBWT3-WF5TR-SC3XW-T333B-TSCTS - The Pre Sequel Heads and Skins (Maya as Nisha)
CTWTB-RXKTR-SKJXW-3TBTJ-KXKKH - The Pre Sequel Heads and Skins (Salvador as Wilhelm)
CJKBJ-3XWTF-HCJ6K-JJB3T-SB35X - The Pre Sequel Heads and Skins (Axton as Athena)

5J5TT-RCJBS-ZXWCJ-TJ3BJ-TK3FB - Salvador Skin
CBKJ3-5FT39-ZRCCT-JTJB3-RFJ5B - Krieg Skin
CBCJ3-W5TT9-S65K3-BJJ3B-XHWWC - Maya Skin
CTKJ3-9CBJS-9R5WT-JBJ3T-WKXKF - Zer0 Skin
535BB-3R3BZ-HF5K3-JJB33-3BF3J - Gaige Skin
KTK3J-FR3JS-ZX55B-B3BJ3-HSRB6 - Axton Skin

WBCJJ-33KWR-S5Z33-BJTTB-65WJJ - Salvador Head
CBKBB-ZHJC6-SWHJT-JJ3BB-3CXHS - Krieg Head
KTC3T-WTW5F-ZCHB3-BT3B3-XJ9WR - Maya Head
CT5BB-XTW5X-9CSBT-3BTTJ-FT5X5 - Zer0 Head
CBKBJ-6ZJW6-HKH3T-B3T33-F5ZRS - Gaige Head
KJKJT-WHBKX-HC9BT-TJBJ3-XJFSJ - Axton Head

WJKBB-KXC3J-5BBCR-5X33J-XZ6RZ - Salvador Class Mod
WTCJT-J653B-C3TKF-5X333-F6JRH - Krieg Class Mod
WJWJ3-FXC33-KT3CR-KR33J-J9B35 - Maya Class Mod
CBWJ3-S5CJ3-WTTCF-WX333-9STBF - Zer0 Class Mod
W3C3B-5JRZC-WJH33-JBJJB-9S6CJ - Gaige Class Mod
5JKBJ-K9WHW-WBZTJ-T3TTB-TW9HR - Axton Class Mod


Golden keys:

K353B-TWSBX-H5BR5-J3T33-6XTCK
5JWTT-KHTSB-S5TXC-BB33J-HCJ6K
5BW3B-F96CT-KXJFK-TB3B3-39BWZ
535TJ-3JC6X-KJXCJ-BTBBT-K5WFR
CT5JB-FSTFX-5TF5T-3JJTT-6CF6T
WJW3B-5HBR6-5BXCT-33TJ3-WXT53
5BC33-CRJRF-WB6WB-3TTTB-655ZX
C35BJ-SRBF6-5TFKB-BBTJT-FSBZK
53K3T-JZJX6-WBXKB-BBJJB-SJH3K
W3CTJ-BFTFR-KJRK3-JJT3J-H6H36
5B5TB-XFBX6-WBXWJ-JJ3TJ-9RXZW
CJ5T3-K5TF6-5TRC3-TBTJB-HZ5ZF
CJ5B3-6TTFF-5365T-TBJBB-SKTCB
KTK3J-JWT6X-KB65T-3JJ3J-WHBRT
C3WBB-W3BRR-5J6WB-3JJJJ-35ZKZ
CJKJB-XWBR6-WJXKJ-JB3TB-WTCWX
CBCB3-SW36X-KJXW3-TTT3J-SFBSB
WBCTT-XX3RK-HK6TB-TTTTT-B5Z53
CTC3J-KR9H5-WTZ3T-TJ3TB-6SRRJ
WB5TT-JFCXX-CBS33-TTTBJ-JJ95B
K3CBT-CRKR6-CB9BT-T3TBJ-595J3
KB53J-RW5XX-539BT-BJT3J-CC55T
KBC3J-95WXF-WBSBT-TTJJB-KTC6K
K3WJT-BFBRW-S5RTT-TBBB3-9XWZ5
WTC3B-Z5ZWC-HW6JT-JJJBJ-9FWXR
K3K33-3W9JT-6XJJT-TB3JB-HWZZF
KJ5BT-FBKSK-KXJ3T-3BTJT-FJX5C
5T5B3-CWJSK-KRTJT-TTJJT-9HW63
CTWTB-JTBW5-KFTTT-JTB33-JTBWB


Source: http://orcz.com/Borderlands_2:_Golden_Key