Scripts for the simple HP and Mana Potion exmple

DestroyAfterTime.cs

using UnityEngine;
using System.Collections;

// Destroys the game object it is attached to after the given timeframe
public class DsetroyAfterTime : MonoBehaviour 
{
    public float DestoryAfterTime = 1.0f;

    void Start () 
    {
        Destroy(gameObject, DestoryAfterTime);
    }	
}

Player.cs

using UnityEngine;
using System.Collections;

public class Player : MonoBehaviour 
{    
    public float speed = 6.0F;
    public float jumpSpeed = 8.0F;
    public float gravity = 20.0F;
    private Vector3 moveDirection = Vector3.zero;

    // The CharacterController component from inside unity.
    // Make sure to add this by making your game object then
    // going to Component->Physics->Character Controller
    CharacterController controller;

    void Start()
    {
       controller = GetComponent<CharacterController>();
    }

    void Update () 
    {
        ProcessInput();	
    }

    void ProcessInput()
    {
        // Check out http://docs.unity3d.com/Documentation/ScriptReference/CharacterController.Move.html
        // for more information on how this works. Basically it reads the user input and then moves
        // the character controller appropriately
        if (controller.isGrounded)
        {
            moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
            moveDirection = transform.TransformDirection(moveDirection);
            moveDirection *= speed;
            if (Input.GetButton("Jump"))
                moveDirection.y = jumpSpeed;
        }
        moveDirection.y -= gravity * Time.deltaTime;
        controller.Move(moveDirection * Time.deltaTime);
    }
}

PotionBehavior.cs

using UnityEngine;
using System.Collections;
using System;
using System.Collections.Generic;

public class PotionBehavior : MonoBehaviour 
{
    // The list of tags that this effect will interact with when triggered
    public List<String> TagsToInteractWith; 
    // The pickup effect to play when this game object is triggered
    public GameObject PickupEffect;
    // If the effect created is attached to the colliding object
    public bool AttachToCollidedObject = true;
    // How long to wait before destroying this object when its not attached
    public float DestroyTimeAfterTrigger = 1.5f;

    void OnTriggerEnter(Collider other)
    {
        if (TagsToInteractWith.Contains(other.gameObject.tag))
        {
           // The effect we create when the pickup is triggered
           GameObject pickupEffect = (GameObject)Instantiate(PickupEffect, AttachToCollidedObject ? other.gameObject.transform.position : gameObject.transform.position, Quaternion.identity);
            if (AttachToCollidedObject)
            {
                pickupEffect.transform.parent = other.gameObject.transform;
                Destroy(gameObject);
                return;
            }
            Destroy(gameObject, DestroyTimeAfterTrigger);
        }
    }
}