Critical Mass at this moment. It barely stretches after flipping which I like so less training needed.. Will be popping some OG Kush next. Anything that doesn't stretch heaps and earlier flowering times (8 weeks or so) I would say is great for indoors. I may do more sativa genetics once I dial in my setup.
Some strains that apparently don't stretch heaps are Green Crack (sat hybrid), Cinderella '99 (sat hybrid), Sensi Star (indica) and Super Skunk / Super Bud (indica), along with some pheno's of Critical Mass.