How I think some things would work in Equestria.

1. Guns : I think they would use magic ammo. Like you fill a clip somehow with a certain type of magic. Pulling the trigger would release the magic. Depending on the magic is what it shoots. Like fire, ice, metal, etc.
2.Cars : I think they would use magic. It could be a fire spell, a wind spell, or whatever spell you want. They would have to be made so that ponies can control them though.
3. ?