Combat tricks are great, but you can't have them work every time. As explained in the GURPS rule book, getting the upper hand in a fight by grabbing a handful of sand and throwing it in your opponent's face might be a great trick to use once. But if it worked every time, warriors would walk around with bags of sand instead of swords.
Actually... that'd make an interesting idea for a campaign world...
Though Anakin would hate it.
(Thanks to Facebook commenter for that last bit.)
Han: Princess! Are you okay?!
Leia: I've just been shot in the arm, what do you think?
Trooper: So sorry. Anyway, about that surrender.
Han: We surrender! We can't survive another warning shot!
Leia: I'll show these guys surrender!
[SFX]: Pow! Pow!
Han: Wow. Best surrender ever.
GM: A walker approaches, aiming its heavy guns at your position.
Han: Quick, let's do that trick again! Okay, I "surrender".
Leia: I surrender too.
Han: What? Who's going to blast them now?