Hitman 2: Silent Assassin

All Weapons
Right, Left, Up, Down, A, Up, B, A.
(Thanks to NORULESWHZZP14@LMF.NET)

God Mode
Right, Left, Up, Down, A, Right, Left, Right, Left.
(Thanks to NORULESWHZZP14@LMF.NET)

Nail Gun
Right, Left, Up, Down, A, Left, Left.
(Thanks to NORULESWHZZP14@LMF.NET)

Silent Assassin Ranks
You can still get a Silent Assassin rank on a mission, if you are spotted. To get a Silent Assassin ranking, there has to be nothing in the aggression bar. Use only chloroform on guards and eliminate targets with one shot.
(Thanks to ninja_man@yahoo.com)

Unlock M4
Finish five missions with a Silent Assassin ranking. OR, earn a Silent Assassin ranking on the St. Petersburg missions. Complete the "Invitation to a Party" for the M4.
(Thanks to ninja_man@yahoo.com)

Unlock Sawn-off Shotgun
Beat any two missions with a Silent Assassin ranking.
(Thanks to ninja_man@yahoo.com)

Unlock Silenced Ballers
Earn a Silent Assassin ranking on any mission.
(Thanks to ninja_man@yahoo.com)