Protoss v Terran: 1 Gate Fast Expand

The key to this build is to scout using your stalkers as you are putting down your nexus, you should have scouted your opponent's position beforehand using a probe earlier on in order to determine the basics of the build they are going. 

9 – Pylon
Chrono Nexus
13 – Gateway
Chrono Nexus
14 – Assimilator
15 – Pylon
Chrono Nexus
17 – Cybernetics Core
18 – Zealot
22 – Warp Gate Research
22 – Stalker
Chrono Stalker
24 – Pylon
Chrono Stalker
26 – Stalker
30 –Cut probes
30 – Nexus
Push with stalkers up Terran's ramp

 The scouting information determines which path you continue with:

Marauder: 1 Barracks Tech Lab Fast Expand

30 – Gateway
30 – Gateway
30 – Assimilator
30 – Stalker
32 – Pylon
Resume probe production
34 – Robotics Facility

3+ Marines, no bunker or reactor already completed: 2 Barracks, Reactor + Tech Lab

30 – Stalker
Chrono Boost Stalker
32 – Gateway
32 – Gateway
32 – Pylon
32 – Stalker
Chrono Boost Stalker
34 – Assimilator
Resume probe production
35 – Robotics Facility

Bunker or reactor building: Many possibilities (including drops, 1/1/1 all-in, banshees)

30 – Gateway
30 – Gateway
30 – Robotics Facility
30 – Assimilator
Resume probe production, Chrono Boost Probes
31 – Pylon
Construct two observers before Immortals, unless you scout an immediate push