What things from the Protoss tech could the Terrans use?
What things from te Terran tech could the Protoss use?
What sort of new war machines could we create?
A ghost carrying psi blades
Wings of Liberty had an entire protoss tech section.
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"Do you hear them whispering from the stars? The galaxy will burn with their coming."
As for Protoss using Terran tech? Easy, Dark Archon mind control says it all.
Yes, that's right! That is indeed ME on the right.
Protoss appear to have no qualms about using terran weapons if the situation calls for it. (Firstborn, frontline)
Also, it's heavily implied that many recent Terran technological breakthroughs were reverse-engineered from captured Protoss tech (even before Stetman/WoL), the original manuel even states that this was one of the main purposes of science vessels.