Dead Rising/Psychopaths

Throughout the game, Frank will encounter Psychopaths - survivors of the zombie outbreak who aren't in the mental state to be rescued. Often, they've taken other Survivors hostage and will attempt to kill them; your only course of action is to take them out first.

The list below is in more or less chronological order, and may contain spoilers.

The Convicts
The convicts are unique among Psychopaths - they'll respawn at midnight each night, with the exception of September 22, and they don't count towards the Psycho Collector, Psycho Taker or Punisher Achievements.

Adam MacIntyre
This clown went insane after seeing the children he was entertaining being killed by the zombies. He now obsesses over the Space Ride that he worked at, and will not allow anyone to stop it.

At the start of the fight, Adam is on the far side of the Space Ride track. Head shots are effective against him, but the best tactic is to run out of the Space Ride station away from Adam and onto the walkways around Paradise Plaza. His dual chainsaws are capable of doing a lot of damage, so you want to keep your distance and shoot the balloons he inflates before he throws them at you; they'll damage him much more than almost any of your weapons can, with the bonus of distracting him for a few seconds to land another couple of shots.

When the fight is over, stop the Space Ride to save Greg, who will open a shortcut for you between the Wonderland Plaza and Paradise Plaza bathrooms.

Raincoat Cult
The Cultists make their first appearance, attempting to sacrifice Jennifer, near the entrance to Colby's Movieland in Paradise Plaza early on the afternoon of the second day. Like the Convicts, they don't count towards psycho achievements, but you'll get a 5,000 PP bonus for every one you kill.

They'll also keep showing up all around the mall up until the A Strange Group scoop at 12.00am on the 21st.

Kent Swanson
Makes his first appearance in Cut From The Same Cloth and shows up again in Photo Challenge, but this time he's got a hostage. Determined to prove once and for all that his skills and commitment are greater than Frank's, he's planning to infect poor Ted with a zombie queen to record the trnasformation process.

If you don't show up quick enough after the scoop kicks off at 12, it'll be too late to save Ted.