I guess it comes down to a couple of things for me: style, steel, quality fit, finish & materials, and customer service.
Style: I can't even predict this! But I like historical or historically based designs ie bowies, nessmuks, hunters in fixed blades. Nothing that's too 'out there'.
Steel: I like SR101, A2, 3V. I haven't tried too much else and to be honest I don't know that I would ever notice the difference. For some reason I have been shying away from stainless steels.
Before I discovered knives properly I used plenty of Victorinox, Green River, Swibo and F. Dick skinners. My favourite was the Swibo.
Quality etc: proven 'brands', good reviews. It's a bit hard down here to get my hands on a knife just to 'try' so I probably don't stray too far from anything established.
Customer service: absolutely paramount. I love Busse and Bark River for this. I have had an absolutely outstanding experience with Bark River recently and they really helped me out. I find Pete Winkler of Cross Knives great too - his knives scream out to me and he is a top bloke. He built my nessmuk and the pictures and updates from the other side of the world during the build made the experience really cool.
To me, the Busse knives that I have are my apocalypse knives. If I had 30 seconds to race out the door I would grab my Ratweiler first, my Cross Knives Nessmuk 2nd and my CG FBM 3rd.