Dancing hostages
You can do this glitch in the "Ghost Dance" mission and, you must have four operatives alive.
First, give every operative a grenade. Then, in the planning screen, make the Blue Team stay put, and make the Red Team go rescue the hostages. Start the mission. The Blue Team should stay at the starting point. As the Red Team, go rescue the hostages. Go to the Island with the big treasure box on it. Next, walk right into the corner where the treasure box is, stop and switch to engage mode. Then, go back to the starting point and grenade the Blue Team. Last, return to where the hostages were and they will be dancing on the island!

Passwords:
Recruit Difficulty VZRFTMQ2G8SQ
All Stages 1ZB1S2Q22MQQ
Mission 2 BJBBC3Q22WQQ
Mission 3 B2BBSMQ22!QQ
Mission 4 CJFCCQQ2FGQQ
Mission 5 CZFCS5Q2F4RQ
Mission 6 DJVDCYQ2FWQQ
Mission 7 D2VDS8Q2F!QQ
Mission 8 5JV2L18GGGS8
Mission 9 Veteran Difficulty 1ZL1S2RF2MQQ
Mission 2 Red Wolf BJJBC3RF25QQ
Mission 3 Sun Devil BZJBSMRF28RQ
Mission 4 Eagle Watch CZBCS5RFFMRQ
Mission 5 Ghost Dance DJBDCYRFF5RQ
Mission 6 Fire Walk LZBDS8R2F8RQ
Mission 8 Deep Magic MJB2D1R2G2RQ
Mission 9 Lone Fox 2ZB2T2R2GMQQ
Mission 10 Black Star FJJFD3R2G5RQ
Mission 11 Wild Arrow FZJFTMR2G8RQ
Mission 12 Mystic Tiger

Example: To be able to play Mission 3 Sun Devil through Mission 5 Ghost Dance,
you would enter the password for Mission 5 Ghost Dance. By entering M12
Mystic Tiger's password, all levels will become available for play.