It all depends on your budget. You can go from a simple thirty dollar dlink or netgear all the way to a nine-hundred dollar Cisco 1252.
I would get the budget for at least a 1131ag AP. As with everything, you get what you pay for. If you buy a Cisco AP, even though they're a lot more expensive, you won't have to worry about messing with them after they're deployed. The last company I worked for who took the cheap route had major issues with their APs. Out of about a dozen deployed, I had to reset two or three on a daily basis.
If you need additional antenna sensitivity, get a 1242. I love this access point from both a looks and performance standpoint. It's got a cool looking dark gray metal exterior with ports that allow you to plug in external antennas.
If you go that route, get Hawking external antennas, or the little 12db DLink omnis. They're cheap and very good.
For security, I'd recomend doing nothing less than WPA2.