I know a small contraption that even an arrow can activate! It requires any amount of the block of your choice, a Redstone Lamp, a Lever or Button (if you want an arrow to be able to activate it, use a Wooden Button), and any door of your choice. Also, iron doors need to receive a redstone signal in order to open; nothing else will open it.
Instructions:
1: Place the door anywhere you want; then place a redstone lamp on top of the door.
2: Place the Lever or Button on the lamp.
3: Surround the door with the block of your choice.
Now to try it out! Activate the Lever or Button. The redstone lamp will light up and the door will open.
PS: Using a bow and arrow to activate it seems like a waste but sometimes it can be pretty fun!