This idea is similar to Weapon idea: Passive effect s
However, I suggest that you can buy specific effects which , when equiped, would provide secondary effect. This can be bought with key.
To be more specific, an additional effect could be like a frost effect. Let say you equipe it on the utensil poker. When you shooting it, you have a chance of freezing a chicken. The chicken would not be completely frozen but would move slower and it attackes would be slowed as well. Other effects could be heat, electric or lighning chain and explosive effects.
Also, where this post suggested, Weapon idea: Passive effect s ,these effects suggested could be weapon specific.