Running Gag: Most of Tim's love interests will at some point try and attack him. Steph was the Trope Codifier in the Robin series. With a brick.
Will They or Won't They? - Tim and Steph have pingpong-ed back with each other for several times since the start of Tim's series. Given that their Red Robin and Batgirl seies ended prematurely with the DC reboot, this was never resolved.
Promoted to Love Interest - was Tim's teammate and close friend in Young Justice and Teen Titans for a long time, but became a love interest when Geoff Johns killed off her boyfriend Superboy ( who was also Tim's best friend) in Identity Crisis.