Complete the game a second time (you must load the once-cleared game file) on Normal or Professional difficulty (the costumes are stored separately with each difficulty) for special costume set 2.
Leon can do some hat tricks with this costume set. I haven’t had the chance to test out how to perform all the moves, but I believe you have to have the Chicago Typewriter weapon equipped to perform these somewhat comical actions (see list below):
Hat Adjust Hold the ready weapon button (B) and perform the reload weapon gesture with the Wii Remote. Since this weapon has unlimited ammo Leon will just adjust his hat.
Hat Toss Hold the ready weapon button (B) and perform a quick DOWN then UP motion with the Wii Remote. This is the more comical of the two gestures, but doesn’t always work; you may perform the Hat Adjust move more often.
Ashley will unlock a metal suit of armor that protects her from any damage and prevents enemies from carrying her away. Now you can leave Ashley were ever you desire in the current area without worrying about her being child-napped.