Them! (1954). Really nice slow build of a monster movie, the first 20 minutes or so being exemplary in intrigue and pacing. It might be giant ant attack, but it's a damn good giant ant attack. Underrated and underappreciated for its direction and writing.
It's 2024, so we should start the year off properly. The Val Lewton-produced The Seventh Victim, classic horror-infused noir with murder, shadows, missing people, the lot.