Yes. Trophies can be unlocked by a group or in solo. It's normally best to buy all weapons by a group to unlock this trophy, to achieve this trophy effectively, follow this method: - Be fair when opening doors, each player should take turns to spend their points when opening doors. - Be prepared to gain many points before going out to buy all weapons. - When ready to buy all of the weapons, use a grenade on a group of zombies (when near to end of a round) and make them legless which will leave you precious time to save running around to buy all weapons (including you and your friends/team mates to spend points towards the doors). You may need about at least `10,000` roughly to spend on doors, and at least `12,000` to `15,000` (from what I remember ages ago). The Collector trophy does not require upgraded weapons or weapons from the mystery box. ---------- This may be quite hard to achieve unless you have a good motivation of escaping and surviving from a large swarm of zombies and also taking them down, be sure to make good use of your grenades for high points when used against a swarm of zombies! ---------- **Optional:** If you may want to test your luck, you can use the mystery box for a good, powerful weapon like the Alien/Ray gun could wipe out a lot of zombies in a few shots (better when upgraded) which will make you *kick ass*! **Tip:** Don't camp. :)