Integral Designs is a Canadian company that specializes in thinking outside the box, or more accurately outside the tent. They do make tents and other gear, but their tarps are truly works of functional backcountry art.
The Guides Siltarp 2 is a sub-pound 8×10 foot piece of Sil-coat, "a high tenacity 30 denier 1.1 oz parachute rip stop nylon impregnated with 1/4 oz of silicone, the lightest waterproof fabric available." Suffice it to say, it's tough stuff, and bonus: it rolls up about the size of a quart (or liter for our northern communist brothers; you keep your free, high-quality health care!) bottle. You need to seam seal the center seam, but it comes with a 1.5oz tube of Sil-Net for that purpose, enough to seal about 40 linear feet.
ID has basically added tie-down points to create an extremely versatile tarp. It has a centerpoint loop for suspension, and velcro on both 8' edges and one of the 10' edges so you can burrito-roll two people in sleeping bags easily. Or, set up as a sit in shelter for four people, or a pup tent for two, or whatever you can think up. It's ability to serve a foursome is where the "guides" designation comes from. It's a high-quality, thoughtfully-engineered piece of gear that might just replace your tent.