This video will show lots of different activities to do with a balloon.  Check it out and give it a try.

This is a great website that you can filter no equipment, how many students, what kind of games, and age.  There are thousands of fun options.  One game that I like to use in PE is "10 second tag". It requires no equipment and only needs a few students to play. 

Here is a link to tons of differnt activities.  At the top of the webpage, you can narrow down what grade level and activity time.  Some games require equipment, but a lot will not.