CRKT First strike, either the military or the smaller one
Cold steel Kubon
KaBar large TDI tanto serrated
Cold steel 4" gunsite (folder)
Spyderco 3.5" endura (folder)
Any advice?
If you go the folder route, get the waved endura 4, the best bang for the buck and has a wave to boot. But you're way better off with a fixed blade.
Regarding your choices, the First Strikes have had lots of reports of absolutely terrible edge geometry, and you want something that cuts. For self defense, I'd go with neither a tanto nor serrated, so i wouldn't go with the that particular TDI. The Kubon is okay, a tanto again, very little finger protection, but cuts well. None of your fixed blade options would make it anywhere near my short list, but that's me. Of the suggestions on this thread, I like Tom Krein's suggestion of the Benchmade best. Also like the CRKT Kaspar/Polkowski Companion if you're trying to save max pennies. Another really strong contender, and probably the best matter separator of the bunch, is the Spyderco Temperance
http://www.knifecenter.com/kc_new/store_detail.html?s=SPFB05 These will be the least cool-looking but best pure cutters of the bunch. Look around, they are on closeout at some places, and can be had for even cheaper than at that link.
If you were to relax your budget a bit, I'd look closely at the Gryphon M10
http://www.elinemerchandising.com/GPM10.html The top edge is not sharp, it's not a dagger, unless Texas would consider an unsharpened swedge enough to be a dagger.
Joe