Riddle me this...

A riddle game. I've seen a few versions of this around (such as The Green Glass Door). Basically, you have a secret rule which the students need to guess. Anything that follows that rule, you like, you don't like anything that doesn't.
For example:
"I like peas but I don't like carrots. I like pears but I don't like apples. I like ears but not noses."
Students need to guess the rule by asking yes / no questions - "do you like beans?" (yes) "do you like pants?" ("no, but I like jeans!") - in this case the rule is to do with spelling - I "like" things with an "ea" in them, and don't like things that don't.
A variation would be getting students NOT to say what the rule is when they have worked it out, but to give extra examples to help the others - generally the smug "I know something you don't know" feeling is enough of a reward. You could use a weak or new student to help you by secretly telling them the rule and they give some extra examples. If students work out the rule, they should keep quiet about it, but
It can be more simple (eg liking things that begin with S, ) or more complicated (words with a double letter, words that contain the letter y - as complicated as you want to make it!)

It's a good game to get students thinking about spelling, or grammar (feminine plural nouns? -ir verbs?)

A variation is to use different language instead of like / don't like. "I'm going to a party and I'm bringing peas. Would you like to come?" "Can I bring carrots?" (no) "Can I bring Jeanette?" (yes) (same rule as above)
or "I'm making soup and I'm adding beans" "Can I add bacon?" "Yum! yes!" "Can I add ham?" "Yuk! no!" (rule = words beginning with B)