You know how in Minecraft you can get a skeleton to miss you, and hit another mob, and then they start fighting? Something similar to that, but you can throw a chemical or scent of sorts at a zombie, and it will have other zombies attracted to, and maybe even fight the fleshy, human-scented zombie.
This could have all sorts of cool scenario’s, including throwing these at mega zombies. Poor and looted players could take advantage of this unique item and its unique ability. There could be basic versions and enhanced versions that have a greater attraction radius (And possibly greater chance for zombies to attack it, not just be attracted).
You could also use these chemicals on enemy players to increase the radius of zombie detection. Since its smell, trying to be silent or hide visually wont help. Smart players could use this as a means of attracting zombies to themselves or an area for farming EXP or loot.
I think this is a realistic (and balanced) idea, where players harness and exploit the zombies for their own gain. Similarly, some of the things mentioned in Molton’s mega-post about suggestions to the game, where I suggested many of his proposed types of new damage, such as acid or the virus, against other players.
Furthermore, it would be very cool if players could extract and exploit resources of acid to use it against other players. It is an all-too-common sight in Zombie Apocalypse movies and shows where one faction may use the virus as a weapon against enemies. Or when medieval Europe was catapulting dead bodies of the infected into enemy kingdoms.