Gimme! lets you quickly borrow sandboxed native objects for safe, prototypal fun. Released under the MIT license

example:

var myString = gimme('String');
var foo = new myString( 'bar' );
var bar = 'hmm';
foo instanceof String                   // false
foo instanceof myString                 // true

myString.prototype.hello = 'world!';
foo.hello                               // 'world!'
bar.hello                               // undefined

also plays well with others:

var locallyScopedGimme = window.gimme.noConflict();