Happy Death Day
The Disastrous Life of Saiki K.
Joel Suzuki, Volume Four: Fable of the Fatewave
One of my favorite scenes in this book was - spoiler! - when Joel inadvertently ended up in a time loop while trying (and failing) to stop Blackspore from getting shot by the Six States ships.
So, there you have it: a baker's half-dozen of some of my favorite time loops. What are some of yours?