A harpoon designed to capture orbital junk has been successfully tested in space for the first time as part of the active debris-removal demonstration mission called RemoveDebris.  

• The pen-size titanium harpoon developed by Airbus engineers in the U.K. was fired into an aluminum target, which extended from the spacecraft attached to a carbon-fiber boom.  
• During the test, it successfully snagged the target out of orbit and reeled it back to the main spacecraft. 

Source: ForumIAS factly