One of the finest psychological thrillers in a while with some interesting insights into the way that the mind works. Momento is a murder mystery about a man with a severe case of anterograde amnesia, meaning that he has no ability to form long term memories, trying to figure out who killed his wife. The main character uses a number of different life hacks to 'outsource' his long term memory and still investigate.
Momento is an exceptionally good example of storytelling in film form, it has all kind of sub plots and twists. The filmmakers do an excellent job putting the viewer in the position of protagonist.