A tailsitter is a type of VTOL (Vertical Take-Off and Landing) aircraft that launches and lands on its tail.
One example of this kind of aircrafts is the Convari XFY-1 (Pogo), which is also the faster Turboprop* aircraft.
*(only in the theoretical world, the faster Turboprop ever made is the Tu-114)
Another example of this kind of aircrafts is the Lockheed (this guys are in all the strange topics)
Another famous Tailsitter, the X-13:
Tu-144, the comercial version of the famous Tu-95:
Always is recommended to make a visit at Loockheed Martin webpage: