I found a great deal on 1.1 Silnylon, under $7 a yard in dark green so I snatched it up and made the biggest tarp I could get without a ridge seam, about 5.5' x 9.5'. Weighed in at 8 ounces.
I experimented with different pitches and found I liked the half pyramid a lot, and disliked pitching this size tarp in standard "A frame". So I decided to go ahead and modify it to pitch a little more roomy. I added a beak for better coverage while sitting up and cooking or whatnot, and I added center tie outs in the back to increase the space inside.
It now weighs 9.4 ounces including the stuff sack I made for it. Compacts into a cylinder smaller than a nalgene.
Being a flat tarp, it's only going to pitch so tight. For these pics I only could locate 3 stakes, so the front corners were being held by a couple rocks and they kept loosening.