GUISkin.font  

// Modifies the font only of the current GUISkin.

var f : Font;

function OnGUI() {
    if(!f) {
        Debug.LogError("No font found, assign one in the inspector.");
        return;
    }
    GUI.skin.font = f;

    GUILayout.Label("This is a label with the font");
    GUILayout.Button("And this is a button");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Font f;
    void OnGUI() {
        if (!f) {
            Debug.LogError("No font found, assign one in the inspector.");
            return;
        }
        GUI.skin.font = f;
        GUILayout.Label("This is a label with the font");
        GUILayout.Button("And this is a button");
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public f as Font

    def OnGUI():
        if not f:
            Debug.LogError('No font found, assign one in the inspector.')
            return
        GUI.skin.font = f
        GUILayout.Label('This is a label with the font')
        GUILayout.Button('And this is a button')