Christina Fulton is another one of Val Kilmer’s heartbroken former costars ... speaking to us about her favorite memories with him.

TMZ caught up with Christina outside the courthouse in Downtown L.A. Tuesday during her legal battle with her son -- and she essentially spoke to the late actor through our camera, thanking him for being kind and generous to her on set for their '91 movie "The Doors" when she was a new actress in L.A.

Catch the clip -- Christina shares more personal words about the lasting impact Val had on her, and it’s truly heartbreaking ... especially since they kept in contact over the years.

She also opens up about her fondest memory with him, which once again takes her back to their time on set together.

Christina acknowledges Val’s legacy is one of the greatest, and offers some much-needed advice to the next-gen of actors coming to L.A. with big dreams like his.

Oh, and of course, she also shares what their favorite movie together is -- so make sure to check it out!