I have always been a fan of A Frame houses. They have a simple, timeless design. Perfect for a home out in the woods away from it all.  Den Outdoors sells plans and kits for building your own A Frame house in a variety of different styles to meet anyone's needs. Check out their site for all the different options.  If I ever build a house in Vermont, this is the design I will be looking for. 

What may be one of the most interesting and original tree house designs I've ever seen, the Pinecone Treehouse is very unique.  The tree house was designed by o2 Treehouse. The tree house is availalbe for purhcase. It is also available to rent on Airbnb. Located in Bonny Doon, California. This would definitely make for a one of a kind vacation.