Someone who tries too hard to fit in with everyone else.
Someone who can't think for themselves.
A fake person. Someone does things to impress people.
A person who wears only "branded" or "labelled" clothing and thinks that it makes them cooler than others.
A person who tries hard to impress other people
Someone who wears two brightly colored collared shirts at the same time and pops both of their collars.
In extreme cases, the tool looks like a Vampire (Count Chocula).
Someone who takes a picture of you on their camera phone when you're copying homework in lunch and threatens to show it to your teacher is a tool. No one likes the tool and everyone talks behind his back.