eager beaver: Always busy working like a beaver tirelessly building a dam, which always annoys a lazy bum like me.
boss's pet: As there are teacher's pets at school, there are always boss's pets at work.
backstabber: Steal your ideas, badmouth you behind your back.
brown-noser: You do the work but he/she gets the promotion. The magic tricks up his/her sleeve - currying favor with the boss