I Want A Rock!

Today, we have the annoying cave-dwelling rock Pokemon that appears every few steps you take (Kinda like a Rock-type Zubat):
Pokemon: Geodude
Ability: They Might Be Giants
They Might Be Giants is an ability that allows the user to change the volume of rocks, without altering their mass. This means he can take a relatively small rock, then increase its size to look really big, but it'll still weigh just as much as a small rock. This makes it useful for creating shields when all you have around you are tiny rocks (The enlarged rocks still have the properties of rock, being tough and hard. Interestingly, the increased volume means enlarged rocks can float on water due to lowered densities). Inversely, the user can take a large rock, and shrink it to reduce the amount of air resistance acting on it, creating a dangerous projectile. It will still weigh as much as a large rock though, so the user can't use rocks that are too large. Geodude uses the rock-enlarging ability to impress the ladies (With fake stunts), and the rock-shrinking ability to perform super vandalism and gain respect among other street hoodlums. Despite this, he does have a heart of gold buried within him...