When you have beaten the game and unlocked overtime mode and got the 5-Day Survivor Achievement the laser sword will spawn in the security room along with your wrestling boots and Megaman outfit.

Get the following achievements in 72 Hours mode to unlock the corresponding ending

Unlock Ending A:
Solve ALL the cases and return to the Heliport at 12am on the 22nd

Unlock Ending B:
Solve ALL the cases and rescue a certain amount of survivors

Unlock Ending C:
Don't get to the Heliport on time and solve ALL the cases

Unlock Ending D:
At 12am on the 22nd be a prisoner of the Special Forces

Unlock Ending E:
Don't be at the Heliport and don't solve ALL the cases

Unlock Ending F:
Fail to collect ALL of Carlitos bombs on act 7-2

Complete the following tasks to unlock the corresponding playing mode

Unlock Infinity Mode:
Obtain the 'True Ending'

Unlock Overtime Mode:
Complete the first 72 hours of Frank's stay in the mall and then return to the helipad by noon on the 22nd

Complete the following tasks to unlock the corresponding playing mode

Unlock Infinity Mode:
Obtain the 'True Ending'

Unlock Overtime Mode:
Complete the first 72 hours of Frank's stay in the mall and then return to the helipad by noon on the 22nd