36″ Clear from Amazon. These balloons are very stretchy, and they are cheap and easy to get. They are an easily and frequently replaced staple in my collection.
Cattex 36″ Long Neck. These balloons are amazingly fun as they grow well beyond their rated size, and can handle a lot of abuse. One thing worth noting is that I have had a very difficult time actually getting the long neck to inflate.
My Inflatable Archive 