The ever popular Mega Man Costume and Blaster make their return in Dead Rising 3, so you can blast zombies in 16 bit style.
The costume and the blaster are unlocked separately, and they will take a bit of work to unlock as usual.
How to Unlock the Mega Man X Costume
To unlock the Mega Man X costume in Dead Rising 3, you just need to complete the main story at least once.
How to Unlock the Mega Man X Blaster
This one takes a bit more work. To unlock the Mega Man X blaster (the best part of the entire costume), you need to complete Dead Rising 3 in Nightmare Mode, and then complete Overtime Mode as well.
Note that you can start Nightmare mode from the very beginning without having to unlock it, and the primary limitation in Nightmare mode is that there are no automatic checkpoints, and you can only save your game in rest-rooms and port-a-potties.