I agree with jim on the 550. I have had the 400,350, 500,550, and 560 and the 550 seems to be the middle ground for me for an edc ZT. If you want to go a different route, the depending on your needs/uses, The 0200 is awesome for a heavy duty work and outdoors knife. The 0400 is awesome if you like tantos, and there is the discontinued 0780 of which like only 300 were made and they are getting real hard to find. It is the smallest zt. There is also the 0700 out there for another heavy duty tanto. Or you could venture into the fixed blades too (0100, 0121, 0150, 0160, and the 0170).
You won't go wrong with the beastly 030x series either! If you feel like spending big money, you could look for the disco'd 0500 mudd knife with sealed pivot and lock, which is my personal favorite right there beside the limited 0360skd. The 0360 skd is a pointier 0350. Click on the link for info and to vote for it!
