Commander

I like to keep a few precons from the same set to have a somewhat balanced power level against each other. Right now I have the Necrons and Tyranids from the WH40k set for this. It also lets you have talking points for how you might make cuts to the deck to make it your own.

Otherwise I think big ramp or midrange makes a good intro. This Molimo Maro Sorcerer deck is an early rev of a budget deck that I would hand over to folks. It goes quick enough to be a threat, but has only a few decisions to make.

Also decks that could run with different commanders in the same color identity in the 99 let's newbies have a bit of control of how they play the deck. An example being [[Heartless Hidetsugu]] and [[Auntie Blyte, Bad Influence]] would play well in either's deck, but changing up the commander choice could cause you to pivot between a combo or agro game plan.

I don't have the deck buit anymore but [[Yeva, Nature's Herald]] was always a good intro deck. You can just focus on ramping and throwing out big creatures or flashing them in at the opportune moment. Let's you explain the difference between instants and sorceries and opens up conversation about how the stack works. Also teaches them about enter the battlefield abilities and triggers.

It's like a weird form of green control that let's you explain how other colors work and most new people tend to be drawn to green from my experience.