Here are the rules. I'll make "koans" out of a list of objects, 3 of them to start, all of which follow a rule I'm thinking of. In comments, anyone can do one of two things:
1) Post a koan of their own, to which I'll respond "That is with buddha" if it follows the rule, or "That is not in the path of buddha" if it does not follow the rule (I may vary my phrasing, but you should get the gist).
2) Post a rule to see if that is the rule I am thinking of. If it is, then I say so. If it is not, then I post a koan to disprove the rule.
In this game, I'm foregoing the "guessing stones" and turn orders since this is meant to be a way for someone to contribute, even if they're just passing through. Also, my house rules for Zendo have always been, "If there needs to be an 'if', 'and', 'or', or other conjunctions (e.g., the koan must contain red items or green items), then the rule is needlessly complicated and shouldn't be used. Implied 'and' with qualfiers (e.g., the koan must contain a red fruit) rules are acceptable."
So, here's the first three koans.
Koan 1: dr pepper, lightbulb, scarf
Koan 2: subway, pepsi, Kleenex
Koan 3: computer, mt dew, paper
[edit: bluelang got it! "The koan must contain a five letter word."]