What is the easiest WoW class for a brand new player?

Site-seeded discussion prompt: new players usually need a class with clear buttons, forgiving defensives, and simple solo play. Which class would you recommend first, and which class would you avoid until someone understands interrupts, cooldowns, and movement?

A good answer should separate leveling ease from endgame ease. Some specs level smoothly but become much harder in keys, raids, or arena.