I'm sure it's not the lightest but the MSR Hubba 2P is glorious inside for 1 guy and all his gear. Especially being able to sit-up nicely on top of your knees when you need to.
What I like about it having the 2P sized floor? If you don't get it quite right when you placed it down in terms of flatness and angle the sleeping bag sits at, with the extra room sometimes you don't have to move the tent anymore, but instead rotate the angle of the bivvy in relation to the tent/floor to compensate and find the least slanted way to stretch out the bivvy.
Definitely pay attention to asking others if they have any problems with condensation INSIDE of the walls of the tents they've suggested to you. My first regular ol REI 1P QuarterDome would have condensation form inside it's walls in some kinds of weather and then drip down and you could end up with gear having some damp spots, or weapons exposed to damp.
First you've got to make the determination of if you can live without a floored tent or not. If you can go w/o floored tent, you've got a lot of options for saving weight while getting good amount of space inside. But, if the idea of those bugs being able to getcha all night long doesn't sound great, so you know you want a "bathtub" style floored tent design, you'll have to really look, and be willing to cough up some loot for lightweight materials of construction.