Daggers need either to be a hollow grind, combined with a professional edge regrind, Like the above mentioned Cold steel Taipan, or they need to be zero-edged like some of the old Gerber Guardian IIs nearly are. Sharpness is essential to cutting outward in fighting...
A great choice would be the Randall Model 2-8 in stainless, as it has all the proper features a dagger should have: Thin slicy edge, despite the narrow blade profile, length, and the light weight of a stick tang.
An even slicier Randall is the Clinton dagger, which is almost like two very slicy 7" knives welded spine to spine... It felt strange to me however, as I just feel daggers should be narrow bladed: Perhaps with a smaller guard I would have liked it better... A broad blade width always felt wrong to me on a dagger: They can be made slicy without width, but it requires either a thin initial edge (which you can then easily touch up), or a very wide professionally applied bevel...: Never try to do the broad bevel by hand yourself!: This is beyond normal hand sharpening, especially doing it evenly four times...
The great advantage of daggers is they are ground four ways, which, combined with a stick tang, makes them the lightest of all fixed blade for a given stock: Typically 20-30% less than a single edge fixed blade. Don't choose a model that ruins this with a full tang, or large, heavy metal guards and pommels...: Kraton or Zytel wrapped around a narrow stick tang is optimal (and usually old and rare now, unfortunately). Slicy and narrow daggers are hard to get there, but it is possible.
Gaston