Claire from "Wedding Crashers"
Rachel McAdams' character Claire is the first and last woman who was able to pin down Owen Wilson's heart in "Wedding Crashers." Though engaged to Bradley Cooper at the time they meet (while Wilson is literally crashing her sister's wedding), the two form a strong connection that forcers her to reconsider her upcoming nuptials.
Landon from "A Walk to Remember"
In "A Walk to Remember," high school senior Landon has no direction until he meets Jamie. She's charming and sweet and they fall in love for the duration of the school year. That is until she reveals that she's suffering from cancer. Her death forces him to reconcile with his choices in life and helps him find a purpose.