Butterfly valves are known to be the most sanitary valve design which is why they are a favorite for home brewing hardware.  These 2inch butterfly valves are able to hold sigifnant amounts of pressure, made with high quality EPDM seals and can easily be serviced if required.
 
Unlike ball valves that have several cavities in them meaning stuff gets stuck inside the valve, butterfly valves are far more sanitary with no "cavities" where dormant liquid can hide and go off.