Primer is a must watch for any one that likes time travel stories. It gets recommended so much and for good reason.
Project Almanac (2015) is another movie I watched this year, and I feel it tried to do a lot of the same things. It's not overall as good, but I feel it's more approachable for less hard sci-fi people and people that Primer made their brain hurt. I enjoyed watching it, so for anyone that's already seen Primer, you may want to check it out.