We are currently working on a science-fiction, single-player mod for Half-Life 2, called Colony 8. This project will put heavy emphasis on realism, so even though it's set on another planet, we plan to create a plausible scenario. Colony 8 will feature:

• 2 Realistic weapon arsenals
• Realistic damage and movement
• A very interesting medic feature, unlike anything you've ever experienced

You can read more about it here