A n00b's attempt at JavaScript code golf...

rock-paper-scissors.js

/* uncompressed - 430 bytes
 * minified (UglifyJS) - 273 bytes
 * FYI - indented using tabs because one character vs 4, yo.
 * Append ?ts = 4 to URL to format this correctly.
*/

function p() {
	var a, b,
	 	m = Math,
	 	r = m.random,
	 	f = m.floor,

		n = {
			r: 'rock',
			p: 'paper',
			s: 'scissors'
		},
	  
		d = [
			{ n: 'r', b: 's', l: 'p' },
			{ n: 'p',  b: 'r', l: 's' },
			{ n: 's', b: 'p', l: 'r' }
		],

		c = d.length,
		w, l;

		a = d[f(r() * c)];
		while (!b || b === a) b = d[f(r() * c)];
  
		w = a.b === b.n ? a : b;
		l = w === a ? b : a;
		console.log(n[w.n] + ' beats ' + n[l.n]);
}