If you want a sheath knife, the excellent SOG 2000 SEAL knife sells at BASS Pro Shops for about $100, or did the last time I checked.

It passed tough Navy trials, as have certain Fallkniven models. www.fallkniven.com Look at the S-1 and the A-1.

Those three should serve you very well. But the Fallkniven will be over $100 from most dealers.

Finally, Ontario has a series of combat knives with synthetic handles that seem like good value for money. I think they sell for maybe $50, but haven't checked in a long time.

How "tactical" do you need to get? The Buck Special, No. 119, costs about $40-50 at some retailers. But it isn't a black knife with saw teeth.