What pocket knife should I buy?

I'm looking to buy a pocket knife for utility purposes, like cutting open packages, letters, etc. I would like a knife that is partially serrated and partially straight edge, and is around 3.5 inches to 4 inches. Price range would be around $15-$30. I would like a knife that is very durable, holds a good edge, and can be sharpened easily and can last for a long time. 10 points to the person who gives me the best suggestion for a good pocket knife that fits my description. Thanks!