Since Giratina can be obtained via GTS, the normal Platinum isn't worth too much. To be fair, I'll trade you a Platinum Articuno I got off the GTS today for it. The shiny one on the other hand is as valuable as a TRU Dragonite at the moment (which I did not yet put on my list since I just got it, not sure if you have the same one though I'll check again).
As for The WCS Milotic....I offer my Shiny Agate Celebi (but must be deemed as NFT if traded)
EDIT: Few others that caught my attention:
-UT JP Southern Island Shiny Latias lv.50 (w/soul dew) *NEW*
-UT JP Navel Rock Shiny Lugia lv.70
I can offer stuff from my shiny list for these since they're not actual events....