All of Sheva's alternates:
And Chris' Heavy Metal and STARS costumes in RE5:
Extra costumes in Killer is Dead:
The Savvy Merchant outfit in RDR (which was actually hard to get):
A Max Payne 1 costume in Max Payne 3:
Chris' yakuza outfit in RE6:
Civilian Marcus in Gears of War 3 was also a great bonus:
Also goes for Cole's Superstar outfit:
I'm probably missing a lot right now, but these are the ones I could think of.