One of the challeges Mark was working on is the Squidgun. It's a living creature you put on your arm, that shoots a long tongue. It will help you get around, as well as eat your enemies.
The Squidgun though is on hold, because I think the Buying system is critical to U4E. The ablity for players to pick the weapons they need for the challeges they face will be a HUGE addition to the mod. And even though some of you obsess about how Buying systems are usually a "Realism" thing, I would like to point that it's really more of a Gameplay Thing!
Think about if for a second. Realism mods are boring and identical, there's little to keep them interesting. They NEED a buying system just to keep the players from falling asleep. It's a great addition to ANY mod, and it will be even BETTER with U4E!
Can you imagine getting access to all of our weapons, whenever you need them??? IT WILL BE INCREADABLE! ;D