That frying pan was a bit ingenious, because it was litterately something he made up in the spur of a moment, and build in like ten seconds while Ms. Merry Christmas looked the other way.
Also it was all the way back in Alabasta, before dials, before Kabuto, before Clima tech.. it was in the beginning.
But it also really showcases Usopp's ability to come up with quick unique solutions in the spur of the moment, like when he threw an alcohold bottle at Kissu, then broke it and lightened it up in flames, quick thinking!
Wrapping wax Luffy, Zorro and Sanji in a robe he soaked in oil and then lith at flame so they would melt, quick thinking!
Using pebber to momentarily blind the enemy and rotten eggs to distract them... not very high tech no, but hey, if it works! And it does.
The thing about Usopp though is also kind of, unlike Franky, he never had anybody telling him how to build things or do things correctly, so really.. he is just guessing himself the way through, which sometimes ends up in some extremely unique contraptions because well.. he had no rules to go from at the get go anyways.
Also remember about the clima tact, which is a pretty funny thing... Usopp never ever intended for it to be used the way Nami used it! Yeah the original clima tact could make cold balls and heat balls.. what ever use they would be in the hand of another, and there was a tiny sprinkler system in it to.. make the enemy slip?
It was how-ever, Nami herself whom could use her knowledge of weather to turn the clima tact into a different weapon and use it in this new unique way Usopp had never even thought of.
Hehe, I think we often forget just how low tech the first clima tact was, just try and rewatch Namis Alabasta battle, it's kind of pathetic.
And then after they found out what Nami would be using and not, Usopp could take out all the useless features to boost the cold balls and heat balls that Nami actually uses to create weather phenomenas.