Log

It rolls down stairs. ("What rolls down stairs...")
It can do this by itself, or two at a time. ("...alone or in pairs...")
It can be used to roll over the neighbors pooch. ("...rolls over your neighbor's dog?")
It's edible when you're hungry. ("What's great for a snack...")
It's the right size for carrying. ("...and fits on your back? It's LOG LOG LOG!")
It's large ("It's LOG, LOG, it's big...")
It weighs a sizable amount ("...it's heavy...")
It's made from natural timber. ("...it's wood.")
It's better than "bad", it's GOOD! ("It's LOG, LOG, it's better than bad, it's GOOD!")