Dexter

There are several keychains featured in this showtime drama about the serial killer with a code Dexter Morgan, played by Michael C. Hall.

1.  Season 1 episode 5.  Dexter is investigating a possible target who is a human trafficker and murderer.  Dexter notices his red floatie keychain, concludes he must have a boat, and comments on it. 
2.  Season 1 episode 8.  Dexter received a note from another serial killer he admires, the ice truck killer, in the form of a doll.  Dexter took the doll's head and turned it into a keychain.
3.  Season 1 episode 10 The police department receives a message from the ice truck killer in the form of a jar of blood, blood he got from his victims.  In the jar is a hotel room keychain.  The police go to the hotel to investigate.