Pariah by Kelvin V.A Allison

Have you ever felt alone? Truly alone?
Try being the last Angel in the world...
After nearly two thousand years upon the face of the Earth, the last Angel Tamiel has nearly gotten used to the loneliness... Allying himself with humans he trusts above all others, he has a very successful business hunting Daemons down and sending them back to the pits.
Life couldn't be more clear cut...
But when the Federal Government come seeking his help, Tamiel soon finds himself up to his neck in rampaging Daemons, insane love sick Cherubim's and possessed Presidents...