This app was mentioned in 2 comments, with an average of 1.00 upvote
Hi, I'm the developer of the GonnyCam Burst Camera app. I upgraded it to use the Camera2 API a month or so ago, and on the Nexus 5 it can do up to 30fps at 8 megapixels, unlimited shots until storage runs out. I haven't tested it on the Nexus6P and the Camera2 stuff is still beta-ish but give it a shot. You have to enable Camera2 in the settings.
This one seems to be pretty good: https://play.google.com/store/apps/details?id=com.samgak.gonnycam&hl=en