Youtuber WeaponCollector has designed a carbine crossbow* and is building it from simply constructed pieces of wood and metal. Just goes to show you how human ingenuity knows few bounds. And hey, Parts 2 and 3 are up already, so give them a look on his channel.
*Note: This video is for entertainment purposes only. I’m not responsible for any construction of the carbine crossbow or any ill-attempted William Tell-type scenarios that occur from use of said crossbow.