Aside from managing your resources, you also need to be able to deal with disasters like Fires, raider invasions, infestations from pesky creatures such as Radroaches and Molerats, or worse - deal with a Deathclaw attack. Your dwellers need Weapons to effectively fend themselves against these threats and stimpacks to heal themselves. You can get weapons from Lunchboxes or by exploring the wasteland. Stimpacks are produced within the vault by building Medical Bays.