i don't know if anyone collects statistics on supplements used by pd'ers but you can look here, can join for free and view their surveys
http://www.patientslikeme.com/

i personally take 1000 I.U. of vitamin D, 1000mcg B-12, combination fish oil capsules, 1/2 multivitamin, 500mg vitamin C twice a day, curcumin, and a few others.

the only supplement i might "feel" any immediate benefit from is american ginseng but not sure if worth the price for the small energy boost i think i'm getting.

a lot of research on the benefits of vitamin e, vitamin c, COQ10 and all found to have no benefit for pd as far as i know, of course have a benefit for general health.

don't think there's any "wow" supplement out there but as with any incurable progressive disease you hope something will help, i think at least 60% of pd'ers when surveyed say they take supplements specifically for pd.