There's a Stealth Boy and lots of ammunition in the armory, which is near the rear of the main room on the left behind a locked "hard" door. Picking this lock will cause MP's to attack, as well as drain Karma and fame with the NCR. If one's status with the NCR is high enough, the MPs will ignore it when picking the lock; Karma will not be affected and the door text will not be red. Marie Pappas, who is in the NCR Embassy across the courtyard. has the key to this door, which can be pickpocketed with a good Sneak skill.