One of the funniest things I ever saw in my life was when I went with my wife to a reunion concert of her old college a-cappella choir. Afterwards they had a little party and a guy got up and did this rhythmic chant - no real melody to it but great for doing with kids. Its a call and response type thing with each line repeated by the "chorus" after the leader says it.

(first get a rocking, hand clapping rhythm going)

I say a BOOM chicka boom
I say a BOOM chicka boom
I say a Boom chicka rocka chicka rocka chicka boom
Oh yeah...
Uh huh...
All right.

Then you repeat several times, each time with a different twist on it which the leader calls out before beginning--faster, slower, higher, lower, happier, sadder, etc. On "sadder" the last three lines are: "Oh no, unh uhh, all wrong."