UserInput.cs

using UnityEngine;
using System.Collections;

public class UserInput : MonoBehaviour {

	public bool walkByDefault = false;

	private CharacterMovement charMove;
	private Transform cam;
	private Vector3 camForward;
	private Vector3 move;

	void Start(){
		if (Camera.main != null) {
			cam = Camera.main.transform;
		}

		charMove = GetComponent<CharacterMovement> ();
	}

	void FixedUpdate(){
		float horizontal = Input.GetAxis ("Horizontal");
		float vertical = Input.GetAxis ("Vertical");

		if (cam != null) {
			camForward = Vector3.Scale (cam.forward, new Vector3 (1, 0, 1)).normalized;
			move = vertical * camForward + horizontal * cam.right;
		} else {
			move = vertical * Vector3.forward + horizontal * Vector3.right;
		}
		if (move.magnitude > 1) {
			move.Normalize ();
		}

		bool walkToggle = Input.GetKey (KeyCode.LeftShift);

		float walkMultiplier = 1;

		if (walkByDefault) {
			if (walkToggle) {
				walkMultiplier = 1;
			} else {
				walkMultiplier = 0.5f;
			}
		} else {
			if (walkToggle) {
				walkMultiplier = 1;
			} else {
				walkMultiplier = 0.5f;
			}
		}

		move *= walkMultiplier;
		charMove.Move (move);
	}
}