Something that would work really well on the Nintendo Wii games console, it would mean a game concept or idea would work particularly well on the Wiimote (the new motion sensitive controller)
A fishin game would be kinda wiitarded but a lightsabergame would be fuckin wiitastic
to find something fantastic or is totally you (William), but only a Will or William can say this to himself. otherwise someone not with the first name William can say as a compliment to the William. Not usually used in sarcasm.
"OMG this is so willtastic!"
"This shirt is totally willtastic."
"That date was so willtastic last night!"