(CustomEventHandler)EventTest.cs

using UnityEngine;
using System.Collections;
using System;

public class CustomEventArgs : EventArgs {
	public string message;
}
public delegate void CustomEventHandler(object sender, CustomEventArgs e);

public class EventTest : MonoBehaviour {
	[SerializeField] public event CustomEventHandler OnCustomEventHandler;
	public void OnEvent () {
		CustomEventArgs args = new CustomEventArgs();
		args.message = "Fuga";
		if (OnCustomEventHandler != null) OnCustomEventHandler (this, args);
	}
}

(CustomEventHandler)Receiver.cs

using UnityEngine;
using System.Collections;
using System;

public class Receiver : MonoBehaviour {
	void Start () {
		this.gameObject.GetComponent<EventTest> ().OnCustomEventHandler += OnCustomEventHandler;
		this.gameObject.GetComponent<EventTest> ().OnCustomEventHandler += delegate(object sender, CustomEventArgs e)
		{
		  print ("OnCustomEventHandler: "+ e.message);
		};
	}
	void OnCustomEventHandler (object sender, CustomEventArgs e) {
		print ("OnCustomEventHandler: "+ e.message);
	}
}

(CustomUnityEvent)EventTest.cs

using UnityEngine;
using System.Collections;
using UnityEngine.Events;

[System.Serializable]
public class CustomUnityEvent : UnityEvent<string>{};

public class EventTest : MonoBehaviour {
	[SerializeField] public CustomUnityEvent OnCustomUnityEvent;
	public void OnEvent () {
		if(OnCustomUnityEvent != null) OnCustomUnityEvent.Invoke ("Fuga");
	}
}

(CustomUnityEvent)Receiver.cs

using UnityEngine;
using System.Collections;

public class Receiver : MonoBehaviour {
	void Start () {
		this.gameObject.GetComponent<EventTest> ().OnCustomUnityEvent.AddListener(OnCustomUnityEventHandler);
		this.gameObject.GetComponent<EventTest> ().OnCustomUnityEvent.AddListener(delegate(string s){
			print ("OnUnityEvent.AddListener: " + s);
		});
	}
	void OnCustomUnityEventHandler (string s) {
		print ("OnCustomUnityEventHandler: "+ s);
	}
}

(Direct)EventTest.cs

using UnityEngine;
using System.Collections;

[RequireComponent(typeof (Receiver))]
public class EventTest : MonoBehaviour {
	private Receiver receiver;
	void OnEvent {
		receiver = this.gameObject.GetComponent<Receiver> () as Receiver;
		receiver.Hoge ("Fuga");
	}
}

(Direct)Receiver.cs

using UnityEngine;
using System.Collections;

public class Receiver : MonoBehaviour {
	public void Hoge (string s) {
		print ("Hoge: "+s);
	}
}

(EventHandler)EventTest.cs

using UnityEngine;
using System.Collections;
using System;

public class EventTest : MonoBehaviour {
	[SerializeField] public event EventHandler OnEventHandler;
	public void OnEvent () {
		if (OnEventHandler != null) OnEventHandler (this, EventArgs.Empty);
	}
}

(EventHandler)Receiver.cs

using UnityEngine;
using System.Collections;
using System;

public class Receiver : MonoBehaviour {
	void Start () {
		this.gameObject.GetComponent<EventTest> ().OnEventHandler += OnEventHandler;
		this.gameObject.GetComponent<EventTest> ().OnEventHandler += delegate(object sender, EventArgs e)
		{
    			print ("OnEventHandler: "+ e);
		};
	}
	void OnEventHandler (object sender, EventArgs e) {
		print ("OnEventHandler: "+ e);
	}
}

(ExecuteEvents)EventTest.cs

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;

public class EventTest : MonoBehaviour {
	public void OnEvent () {
		ExecuteEvents.Execute<IReciever>(this.gameObject, null, (x,y)=>x.OnExecuteEventsHandler("Fuga"));
		ExecuteEvents.Execute<IReciever>(
			target: this.gameObject,
			eventData: null,
			functor: (x,y) => x.OnExecuteEventsHandler("Fuga"));
	}
}

(ExecuteEvents)IReceiver.cs

using UnityEngine.EventSystems;

public interface IReciever :  IEventSystemHandler {
	void OnExecuteEventsHandler(string s);
}

(ExecuteEvents)Receiver.cs

using UnityEngine;
using System.Collections;

public class Receiver : MonoBehaviour, IReciever {
	public void OnExecuteEventsHandler (string s)
	{
		Debug.Log("OnExecuteEventsHandler: " + s);
	}
}

(UnityEvent)EventTest.cs

using UnityEngine;
using System.Collections;
using UnityEngine.Events;

public class EventTest : MonoBehaviour {
	public UnityEvent OnUnityEvent;
	public void OnEvent () {
		if(OnUnityEvent != null) OnUnityEvent.Invoke ();
	}
}

(UnityEvent)Receiver.cs

using UnityEngine;
using System.Collections;

public class Receiver : MonoBehaviour {
	void Start () {
		this.gameObject.GetComponent<EventTest> ().OnUnityEvent.AddListener(OnUnityEventHandler);
		this.gameObject.GetComponent<EventTest> ().OnUnityEvent.AddListener(delegate(){
			print ("OnUnityEvent.AddListener");
		});
	}
	void OnUnityEventHandler () {
		print ("OnUnityEventHandler");
	}
}

BroadcastMessage.cs

this.gameObject.BroadcastMessage(methodName, argument);

SendMessage.cs

this.gameObject.SendMessage(methodName, argument);