Lightweight tent recommendations?

Hi,

Does anyone have any recommendations for a lightweight one man tent. I was thinking of 1kg, probably for summer/Autumn use only.
Or, do people think a bivvy bag is better?

Ives, pls expand: budget? height? terain use = freestanding? inner pitch first? etc...

unless you like condensation, feeling like a battery chicken, forget bivi.
I like Akto, T-N Laser, Tarptent