Nagel's has the best selection, but they are crazy overpriced. They've also got a lot of consigned knives - still crazy priced. Crazy people work there as well. Although the girl in charge of the knives is pretty nice (I think she's the owner's daughter). It's one of the only places in town to see CRKs, Striders or Randals.
There's a place called "Top Brass" on 1-10 near Huebner that's got a great knife selection. They've got Spyderco, Becker, Cold Steel, Kershaw, ZT, Benchmade, etc. They DO NOT have any Strider or CRK. It's relatively new and I dropped by there on accident one day. They've got an awesome selection of guy stuff (maxped, spec op, condor, etc.) and your standard army surplus kind of stuff. A little north from there (at the corner of 1-10 and De Zavala) there is an outdoor store that also has a pretty decent selection of knives and climbing/hiking gear (can't recall the name). It's in the same strip center as Einstein Bros.
Bass Pro is okay, but not as interesting as Top Brass. $85 for an American Lawman at Bass Pro is way too high. Pretty good selection - don't let them sharpen any of your knives. Lots of other cool stuff there too. I personally like Cabela's better. It's right outside of Austin and will take about an hour to get there from SA. Truth be told, they are very similar stores.
It's hot as hell here right now. Have a good time and I'll put up some other stuff if I can think of anything.