Hide in the massive castle walls of the toilet paper section, then jump out and yell "Get outta my yard!!!" every time someone walks through the aisle. (I've done this.)
Throw various objects over the top of your aisle into other aisle. Then, swiftly walk away. (I haven't done this, although I've been tempted.)
Have yelling arguments with yourself, or a friend in another aisle.
Shopping cart jousting (pool noodles are the preferred weapon of choice).
Build stuff out of the various boxes of dry/baked goods lying around.