*I Am Going On a Picnic...*
You tell the class that you are going on a picnic and you are bringing a... (chose something that begins with the first letter of your name, but don't tell them this is what you are doing. For example, someone named Sarah might bring Sandwiches). Tell the class that you would like them to come on the picnic, but they can only come if they bring the right thing. Let them ask if they can bring this and that, and tell them that there is a secret trick/pattern to the game that they need to figure out. For example, if Freddy asks if he can come and bring Oranges, you say "Sorry, but no". However, if Jennifer asks if she can bring Jellybeans, you would say "Why yes you can come and bring Jellybeans, Jennifer". Keep going in this manor until someone many people are coming on the picnic, and people are starting to figure it out. You can switch up the game by then making it so that people can bring things in alphabetical order, or only things in one particular food group, etc.
I have also done "I am going camping" with the same rules.