Capstone and Ingersoll-Rand NG turbines seem to be in favor these days among the paranoid.
http://www.capstoneturbine.com/
http://www.irpowerworks.com/
These may be up to 2x the cost of a diesel, but they run forever, you can put them anywhere, they always start, and the fuel never gets fouled. For installations large enough to care about tank pressure, heaters are an option, but then there's the question of how you power the heater... 
Regards,
Andrew Bender
taqua.com