I love it. It will always have a soft spot in my heart because of
Rupert Giles from "
Buffy, the Vampire Slayer". :)
I do think it's usuable, because it's quite similar to
Miles (in sound and appearance) - and
Miles is a fairly popular name in my eyes.
As for combo ideas, here are a few of mine:
Giles Ambrose (my favourite!)
Giles CuthbertGiles DesmondGiles EdmundGiles EdwardGiles HenryGiles LeopoldGiles LudovicGiles MontgomeryGiles OthnielGiles Roman
I think any middle names starting with S- are out of the question with
Giles, because
Giles has a fairly long 's'-sound at the end and that will overlap with the 's'-sound of the middle name. To each their own, of course, but to me that isn't an attractive thing.