From PsychoSilverTH at ZDoom forums: A mod with the property of unlock skills and upgrades weapons like increasing damage, increasing speed of projectiles, unlock unique abilities of weapons ETC, kill your enemies earn exp and money, boss fights, and much more!
For any questions, please visit the official thread here:
Forum.zdoom.org
The file uploaded here is now out of date. The author has made a moddb account to post the new version, you can view it here:
Moddb.com