After death?  

Leonardo da Vinci
His glider design predated man's flight by some 400 years.
http://www.cronaca.com/archives/000416.html

Thanks Brent
Da Vinci is a good one, however I was trying to remember the famous modernist designer from the 50s whose design coundn't be made until recently. Just can't remember who it was.
S

Are you thinking of the...
Are you thinking of the Bertoia Asymmetric Chaise, by any chance?
http://www.knoll.com/products/product.jsp?prod_id=707&flag=cat&cat_id=18

Is it the PK0 chair?
Did you mean the PK0 chair by Poul Kjaerholm?

I think I found the one
It was the Eames Chaise. Or so i am told.

prouvé? i believe...
prouvé? i believe definitively one of his design coming out this year that wasn't produced during the designers live.