Get something somewhat responsible...a low weight but decend hp, 2 door, 2 seater CRX will cost them a lot in insurance expecially for a 16 year old driver. You get any tickets and it gets much worse for them.

You want to get into cars start with something like a Civic sedan where you get a longer and wider wheelbase than a CRX (makes it safer for rookie drivers), small engine but can be modified (slowly) as you gain experience, can be a swap candidate in the future if you get really into it, they are reliable and well built, and since they have 4 doors there's more room for friends to fit in there for road trips. Plus picking a sedan show's your parents you want to be safe. But Civic Sedans can be very fun to drive and modify if you go down that road.