Two weapons can be equipped at a time (primary and secondary). Primary weapons have unlimited ammo and secondary weapons have limited ammo. Secondary ammo can be replenished at certain checkpoints, as well as from Power Ups that are dropped randomly by killing robots.
Weapons can be purchased using nuts (dropped from dead robots), loot crates, and mission completion rewards. Weapon coupons are dropped in loot crates and at random by certain robots. Finding a weapon coupon makes it available for purchase in the store.