I generally carry a couple of knives at work. Currently, I have a old and beat up Spyderco Police with G10 scales that I carry in my left side cargo pocket. I use it purely for cutting things like plastic ties, paper, boxes, etc. You know, what a knife is meant for. I also carry a knife in my right hand pocket which is generally a bit sturdier and can be used for heavier work. Currently that is either a BM Skirmish, or a Spyderco Manix. I keep a Spyderco Civillian clipped to my armor.
If I was going to carry just one knife, I would want to carry something that was durable, sharp, and cheap enough that I wouldn't be overly concerned if I either broke it doing something stupid (prying open a window for example) or lost it. Beyond a doubt my reccomendation would be for the Endura. Fantastic knife for the money. Light, sharp, good steel, and cheap. For a higher dollar option, and a bit bigger knife, the Manix gets my vote as perhaps the best working knife I have handled.
The Emmersons I have handled, while nice, just didn't seem worth the money asked for them. But that is a small sample of knives, all of which were owned by police, whom I'm sure your are aware, can break an anvil with a rubber mallet. No doubt they were much nicer when new.