Chromag Phase 30. Best rims I've had. Broke 3 rims (XT, Flow mk3 and Giant carbon) before running these. I've beaten the snot out of them on my hardtail for the past 18 months and, apart from an initial re-tension after the first couple of rides, haven't touched them. No dents, stayed true. Highly recommended.
I know a few people that run the beefier one (BA30) in the back too for a bit of extra security. I haven't felt the need though