Maybe it was due to my upbringing; my father showed me about knives. He always had a good sharp one in his pocket, and I am no different. But working around the house and being a cop are different job descriptions.
I recommended a good police utility knife to the reader who called me. One that has a combination blade: a serrated and traditional blade combined in one. What is important here is the term "utility knife," not tactical or fighting knife. I am speaking here of a folding knife that fits into a sheath or pocket. I am not talking about a straight blade knife worthy of a mercenary.
Administrators will appreciate this distinction, as will trainers. In the daily grind of police work, you will need to cut crime scene tape, packing evidence, and so forth. The serrated blade can be used for cutting seat belts, ropes, or other heavier tasks. Follow your departmental guidelines here. Some describe these folders as tactical knives, so again check your rules.
Multi-tools
When these came upon the market, I think every cop wanted one. It was a toolbox that could be easily carried on the belt or in the ready bag. I cannot recall how many times I have used mine. These pliers combinations are nearly required in your boat, camping equipment, car glove box, and so forth. They make sense for street cops to have for those special needs.