Directly using "line":
* The Thin Red Line (1998)
* The Line (1998)
* The Line (2001)
* The Line (2018)
* The Line (2023)
* Line of Duty (TV series, 2012-2021)
* The Front Line (2011)
* Line of Sight (2000)
* The Line of Beauty (2006)
* The Last Line (2023)
Containing "line" in a compound word:
* Deadline (1993)
* Deadline (2000)
* The Deadline (2009)
* Baseline (2013)
* Timeline (2003)
* The Time Machine (2002) (contains "time line" within the story)
* Headline (1990)
Other examples:
* The Straight Story (1999) (although "straight line" is a concept rather than a direct phrase)
* The Thin Man (1934) (though "thin line" is implied, it's not a direct phrase)
This list isn't exhaustive, and there might be other movie titles that use "line" in a more subtle way.