Yes, M.R., "Primer" was and still is a "Rare Gem" of that...Genre(shall we say?), I have viewed it probably a half-a-dozen times or more with friends at "Primer Parties" - where we actually "Pause Playback" for discussions and dissect the movie in fine detail.
Two other movies, in a similar vein, that you may also possibly enjoy - at least I did, and still do enjoy - and that I heartily recommend, are :
- "Frequently Asked Questions About Time Travel" - :
http://www.imdb.com/title/tt0910554/
- "Summer Time Machine Blues" ("Samâ taimu mashin burûsu" original title) - :
http://www.imdb.com/title/tt0498567/
Nowhere along the lines of that "genre" of movie, and at the risk of being somewhat "off topic"...
One of, if not, the best movie, from my perspective, that has been Released, in the last 10 or 15 years, is an Australian Film that flew well under the radar of most movie goers.
An Awesome movie titled "Red Dog" :
http://www.imdb.com/title/tt0803061/
Derek Zoolander said:
Fully 83% of the people who watched "Red Dog", voted it "Best Movie Ever"...the remaining Three-Quarters of the people voted it "Bester Movie Ever"...Think About It!
- ^^purely fictional creation - not an actual quote^^ -