Copied this strategy from a ladder game a couple of months back. It's very strong against standard play, especially vs Terran and vs other Protoss, vs Zerg not so much. It can beat the Marine SCV-Allin too.
2 Gate Zealot pressure, i dunno, it'll work perhaps.
I did this strat vs drew's zerg today, i messed up the build which as a consequence failed hard but don't write this strat off, give it a try
i did some other games, vs gendarme, vs other players and vs the AI

i also messed up by ending up having a stalker trapped between buildings...
The start is simple, yet effective.
The build doesn't look too different from standard play, but you get everything faster.
If people don't know how to read the time when they scout you, they won't even see it coming.
Our aim is to get 5 stalkers to our opponents base by 5:25ish, at 5:15 you have exactly 5 stalkers if you did the build right, which is quite a good early force. Stalkers are fast, have shields and thus are a great harass unit.
8/10 Pylon (don't build any probes until you warped in your Gateway)
8/10 Gateway Scout now if you seem it's necessary
9/18 resume probe production and Chronoboost it right away
10/18 Assimilator (when finished, put 3 probes in it)
12/18 Cybernetics Core
From here on, cut the probe production
12/18 2nd Gateway
When the Cybernetics Core is finished, research Warpgate tech and Chrono Boost it continuously. Scout now if you didn't before
12/18 1st Stalker
14/18 2nd Stalker in Gateway No. 2
16/18 3rd Stalker in Gateway No.1
16/18 proxy Pylon
As you play along, always Chrono Boost the Cybernetics Core so the Warpgate Tech finishes in time
18/26 Warp in 2 Stalkers at your proxy pylon, which make a total of 5 Stalkers
Attack!!!
Immediately Chrono Boost the 2 Warpgates, when they are ready again warp in 2 additional Stalkers
Build a Pylon in your base and resume probe production
At this point, you can do whatever, but be sure to use the Stalkers to their potential.
In my games, i neglected scouting, but you shouldn't. After you've planted your first or your second Gateway, scout your opponent, especially on 4 player maps to see on which position they spawned.