Benchmade just launched the new 5400 Serum which features the AXIS Dual Action Mechanism. It offers redundant opening mechanism. The primary is an auto opener with a standard thumbstud opening and AXIS blade lock.
You pull down the AXIS button for manual opening and pull a little further to the rear for automatic opening. This means that even if your spring breaks for some reason, you can still reliably open and close your knife.
This 3.47″ blade is made of Elmax premium steel (58-60 HRC). The 550 Serum also features G10 scales with full stainless steel liners and a reversible pocket clip.