Fighter. There are a lot of feats to choose, but those choices can be made so everything is already written onto the sheet. The Weapon Focus feat chain can be calculated on the character sheet ahead of time, so all the new player needs to worry about is "walking up and hitting the guy".
When you run out of feats for Longsword you can switch over to Longbow and keep going. This isn't the most exciting build and not the most efficient but it would likely be the best for a newbie. You want the player to be worrying about understanding Saving Throws and how attacks work instead of if a spring attack is the best choice at this point.
On the other end of the spectrum I would say ANYTHING with magic would be the worst for a new player. When a player is learning about skill checks the last thing they need is approximately 27 billion different definitions of "level" thrown at them. Even a Sorcerer with simple spells picked out for them will have to worry about the area for a fireball or if they have the expensive matrial components for the spell and you don't want a new player to have to wade through the half page listing for Dispel Magic in their first session. There are an awful lot of numbers to throw at a new player with any spellcaster not to mention the sheets worth of numbers for any character.
Keep it simple - this by definition means no magic. Maybe after they get the hang of the basics (2 or 3 sessions in) they can try a spellcaster.