As with previous titles in the Resident Evil series, Resident Evil 6 features a host of collectible items for you to discover throughout the game and unlock.
In addition to the serpent emblems and tags—which you can unlock by simply playing the game and performing various feats (e.g. shooting zombies in the head with a certain weapon) or in the case of the following unlocks, you'll have to complete each of the game's four campaigns and play through the Mercenaries mode and acquire S rank in the stages.
Some of the outfits for the female characters make them look like they belong better in a strip club than in an action game.
You'll have to unlock each and every costume (every character has one) to unlock Carla, so keep that in mind.