Buddy club P1 Racing QF 17x8 ET45 front and 17x9 ET63 rear weigh in at 13.4lbs and 14.4lbs rear here's mine:
There's a few others too (from memory):
Volk CE28N 14 & 15lb
Volk TE37
Mugen MF10 14 & 16lbs
BBS forged OEM in 16"
Spoon SWS
This car has extreme offsets so make sure you investigate it fully before ordering and double check which tyre width is required to prevent rubbing.
Oh and if you're looking to reduce unsprung weight then i'll assume you're more focused on performance rather than 'bling' so stay with 17's maximum to retain the handling. Also note that the larger the wheel, the heavier the tyre due to increased sidewall weight and the benefits are diminished further because the mass is towards the perimeter of the wheel/tyre. Toyo tyres tend to be the lightest too...HTH