If your opponent is Pi$$ing you off, or if you want to piss him off this is a great way to do that.
Ok, the first thing you do is get 2 High Templars (that know psionic storm and hallucination) and 1 Shuttle. Before you load the High Templars, make one High Templar hallucinate the other (understand so far?). Now load your High Templars (including the hallucinated ones) into the Shuttle and drop them behind your opponents mineral supply. Now here is the fun part, take you 2 NON-hallucinated High Templars and use Psionic Storm on there SCV/Probes/Drones until you can't use it anymore(works best against Drones). Now you opponent probably wants to kick you @$$, but your not finished. If you were quick enough, you should still have your hallucinated High Templars, put theses in front of your "other" High Templars (so your opponent will attack them first :P ). Take your 2 High Templars and and make them "morph" into Archons. When you got your Archon, your Hallucinated High Templars should be long gone. Now just sit back and watch you opponent deal with your Archon :).
Since your opponent now has a lot of work to do (getting back his SCVs/Probes/Drones) you have time to make an attacking force and kick your opponents @$$.

>>>>>>>>>>>>>>>>>>>>>>>>*NOTE*<<<<<<<<<<<<<<<<<<<<<< If you want this to be more affective just get 2 more High Templars and 1 more Shuttle and do the same thing.

CreepColony's Opinion: Umm...I'm not sure why you would want to waste your time doing that hallucination/archon thing. Just a psi storm would do the trick.