A lot of SWAT and infil. guys will tell stories about the sound of just
racking a pump-action shotgun will convince many hardened guys to give up.
Handgun-wise. A good .45 cal. is what you want. No need for some .50 Desert Eagle or other hand cannon. My personal pref -- H&K USP .45. The Glock .45s are nice, and I know a number of 1911 fans hereon will extol their virtues. But if our special forces guys carry H&K .45's (slightly modified from the USP you can get in your local gun shop) it should be good enough for you.
JP