First Person Controller

Let's make simple first person controller, that will let us move around level in first person mode. Start by making empty game object and call it FirstPersonConttroller, then add character controller component to it. This will represent body of our character, but we still need head so we can see anything. Your scene should already have camera, drag it on top of your newly created FirstPersonController in Hierarchy tab (on the left) so it will become child of it. Then, position it so it's in the center and a bit above (where head should be). When you are done, it should look like on this picture:

Next, create new script and add it to your FirstPersonController

using UnityEngine;
 
public class FirstPersonController : MonoBehaviour
{
    public Transform head;
 
    private CharacterController cc;
 
    private float pitch;
    private float yaw;
 
    public float speed = 6.0F;
    public float jumpSpeed = 8.0F;
    public float gravity = 20.0F;
 
    private Vector3 moveDirection = Vector3.zero;
 
    // Use this for initialization
    void Start()
    {
        //Initialize various usefull things
        cc = GetComponent<CharacterController>();
        pitch = head.transform.localEulerAngles.x;
        yaw = transform.localEulerAngles.y;
 
        //Let's hide lock cursor so its not going outside the window
        Cursor.visible = false;
        Cursor.lockState = CursorLockMode.Locked;
    }
 
    // Update is called once per frame
    void Update()
    {
        if (cc.isGrounded)
        {
            // If we are touching the ground, calculate movement and jumping
            moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
            moveDirection = transform.TransformDirection(moveDirection);
            moveDirection *= speed;
            if (Input.GetButton("Jump"))
                moveDirection.y = jumpSpeed;
        }
 
        // Always apply gravity
        moveDirection.y -= gravity * Time.deltaTime;
 
        //Move our character
        cc.Move(moveDirection * Time.deltaTime);
 
        //We rotate whole body when looking around
        yaw += Input.GetAxis("Mouse X") * 10;
        transform.localRotation = Quaternion.Euler(0, yaw, 0);
 
        //But only rotate head when looking up and down
        pitch = Mathf.Clamp(pitch - Input.GetAxis("Mouse Y") * 5, -70, 70);
        head.localRotation = Quaternion.Euler(pitch, 0, 0);
    }
}

Next, we have to show our FirstPersonController script where our head is. With FirstPersonController oject selected, drag your head (Main Camera) into 'Head' property of your script, as in following picture.

Congratulations, you now have fully working first person player controller. Add some geometry to your level and test it!