actually is it possible to make a person slide or walk through a sloping surface?? any example?
The 3D Platforming example might be able to help you out with this! The Thirdpersoncontroller script allows this.
http://unity3d.com/support/resources/tutorials/3d-platform-game
The Unity Locomotion System also can help: http://unity3d.com/support/resources/unity-extensions/locomotion-ik