Gearwrench’s Roto Ratchet is a flex-head swivel ratchet with a pivot through its drive head. This design enables the Roto Ratchet to be positioned perpendicular to a fastener to apply maximum torque, axially aligned for rapid spinning, or any angle in between.
Gearwrench’s Roto Ratchets are available in 1/4″ and 3/8″ drive sizes, and a set of both will set you back about $50-$60.
This style of swivel ratchet is also available from other brands such as Snap-on, and Harbor Freight. The Kobalt version that can be found at Lowes is essentially the same tool as above, but with a different grip.