Some kind of dagger, with sturdy blade capable of slashing and stabbing.
Maybe something along the lines of Cold Steel Shanghai Warrior/Shadow. I have Warrior, its a huge 10 inch blade with big bellies and pomme, wide and stiff, with sturdy point. The downside is its huge and rather heavy, concealing it is out of question and and many will find it too cumbersome for open carry on the belt. You will get some funny looks from other people too, because this fucker is really like short sword.
The Shadow is smaller and lighter, made from a worse steel, but if you only want it as a weapon it makes no difference. Either will be capable to gut the doggo.