A person who is a rogue, a scoundrel, or a real piece of work. It is used to describe someone with a shady reputation or who is known for being tricky and untrustworthy. (The word ficha refers to a police record or a profile, used here sarcastically).
Oh man! Eres una buena ficha. You do not have a good reputation.
A vulgar insult describing a person who figuratively chews on someone else's testicles, used to call someone a sycophant, a brown-noser, or a contemptible individual (grano is a common Dominican slang term for testicle).
Look, you Maca Grano, get away from me before I slap you.