PrimitiveType.Cylinder  

function Start () {
var cylinder : GameObject = GameObject.CreatePrimitive(PrimitiveType.Cylinder);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Start() {
GameObject cylinder = GameObject.CreatePrimitive(PrimitiveType.Cylinder);
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Start():
cylinder as GameObject = GameObject.CreatePrimitive(PrimitiveType.Cylinder)