Terran Vs. Protoss
Defending
*Just like against Zerg Firebats are important, but build them against massive Zealot rushes. Against other units they aren't worth it. Put the Bats in bunks and they will kill the Zealots like dogmeat.
*Science Vessels are very important! EMP Shockwave is your best friend vs Protoss. It will take away their entire sheilds. It is useful for defending and attacking
*Ghosts are not as important since they are overpriced but they will still be good to Lockdown an Arbiter, Reaver, Carrier, etc.
*Build Turrets ALL around your base. The last thing you want is a Reaver drop in the middle of your base.
*If they are using Arbiters to cloak their armies use a Yamato gun to take it out.
*If by any chance a moron is making Archons and attacking you with them use EMP and they will have 10 hp(hit power).
Attacking
*Use cloaked Wraiths to attack a Protoss players heart, their mining industry. Kill all their Probes but if they have an Observer Comsat the area, find the observer(s), and kill it/them. This will NOT work if they have Photon Cannons surrounding their minerals.
*Many times Protoss players build a bunch of Cannons in the front of their base. If you plan on attacking through that way then EMP Shockwave will make the Cannons a sinch to kill if you have some Seige Tanks attacking also.