If you work in a warehouse or in any sort of material-handling job, a utility knife can be your best friend, or it can send you to the ER. Martor USA makes a series of utility knives, including the Megasafe 116003, that features a blade-retraction mechanism — the blade automatically snaps back into the knife’s body when it loses contact with the material it’s cutting. This reduces the risk of accidental injury by making sure the blade is only out when it’s under control.
The Megasafe’s aluminum, ambidextrous handle contains the patented “smart knife technology”. Essentially, a spring retracts the blade once tension is taken off, regardless of the blade slider’s position. You can get the Megasafe in two versions, one with a .30mm blade and one with a .63mm blade. The former model works well for slicing through lighter materials, and the latter is for heavy-duty jobs.
You can find ’em for about $20 — but don’t completely rely on the Google product search, as selection there is pretty slim.