Knives
Depends on your personal taste with knives, how your trained with a knife,where it's going to be carried, and the quality your looking for.
My main suggestion is get some sort of training with edged weapons before using one as a back up.
My suggestion is Escrima, Kali, Arnis, or Mr. Hockhiems course.
My suggestions for a folder is to get someting that can be opened with both hands no matter which hand your using. (Spyderco or Bench Made)
Fixed blade it's your choice. My choices are as follows:
Surplus bayonet, Ice Pick, Craftsmen heavy duty screwdriver, benchmade, good paring knife, Bowie, K-Bar, and good metal machined pen.
And if your LE. I'd go for a Bench Made Switch Blade or a good German one. I tend to avoid the 5$ Tijuana specials.
I personally try to keep everything as utilitarin as possible.
Hope this gives you some help.