A boxy, medium-sized Starfleet shuttlecraft introduced in the fifth season of The Next Generation and carried by the Enterprise-D and later by Voyager, with room for two pilots and several passengers.
The Type 6 is the shuttlecraft most often seen in the later seasons of Star Trek: The Next Generation. It first appears in Darmok, when Worf takes one down towards El-Adrel IV, and it replaced the larger, curved Type 7 as the usual full-size shuttle on the Enterprise-D. The studio prop was rebuilt from the shuttle made for Star Trek V: The Final Frontier.
Enterprise examples include the Goddard, which Picard lends to Montgomery Scott at the end of Relics, and the Justman, seen in Suspicions. They are warp-capable and lightly armed, and are used for everything from survey flights to diplomatic errands.
The USS Voyager carries the type as well, and loses several in the Delta Quadrant in the early seasons of Star Trek: Voyager. The Lower Decks shuttles of the USS Cerritos are a development called the Type 6A.