Ok, how hard would it be for someone to create a mod for HL that would allow a trigger to turn a player into a chicken? Ala Heretic.
I haven't played that game in years, but the Chicken Egg was one of the most original ideas then, and I haven't really seen it done well since.
I figure if someone could do it back then, it can't be too hard to do today.
I'm thinking you could have an egg gun, which fires eggs like a grenade launcher and when they hit someone, they turn into a chicken.
I have no idea how to get the models made and how to get the thing to work in HL.