The wizards duel. It may have had zero CGI, and only lasted for a few moments but. Damn in those few moments Akiro was totally BADASS!
If you watch closely, you can see how much effort the wizards exert in the duel; smoke comes out of The Leader's nose at one point, and at the end, it looks like steam is coming off of the victorious - and visibly exhausted - Akiro. Hardly any visual effects in that scene, but it's the acting of Ferdy Mayne and Mako that make it work.
Conan's cunning and crafty defeat of the Guardian, the wizard Thoth-Amon, along with Awesome Music was pretty damn epic.
Conan's final fight with Bombaata was pretty impressive.
Dagoth, the (semi) resurrected god of evil v.s. Conan:
Winner = Conan
Want a real subtle Dagoth CMOA? They needed an actor that was physically imposing enough to tower over Arnie, strong enough move with giant layers of rubber costume on, AND still able to put up a convincingly choreographed fight? Who could do such a task? André the Freaking Giant. Who went totally uncredited for the role for years.