Thor and Usopp - adding to the theory
My little theory here about my favourite character, my dear dear Usopp! I know it has been treated but I wanted to dig a little deeper with the details I got from some researches.
He wants to prove he is a brave warrior of the sea. Everybody is seeing him getting Ragnir and I second that. Not because he got stronger, but because he is brave - in the Marvel comic, Mjolnir only responds to people who are brave enough, not the ones who are strong. Mjolnir comes back in the hands of the one who threw it, which could make the link between Usopp's ability as a sniper. That was said by many fans.
Here is where I want to add some points.
Thor is, in the mythology, the god of the humbles and the craftsmen, people like Usopp ; of fertility too - think of the pop green. Thor is known to lie (not as much as Loki though) to get what he needs : for example, he had to disguise himself as a bride (with Loki as his bridesmaid, which is hilarious btw and would be awesome in Elbaf) to get back Mjolnir. Thor has a belt he needs to use Mjolnir - think of the belt of Usopp. Thor is associated with goats that push his cart, goats he can revive - think of the Going Merry. In Syrup village, Kaya lives in the biggest mansion of the island - Thor lives with his wife in the biggest house of Nordic Mythology. Thor and Herakles are often mixed in Mythology : who trained Usopp? Herakles.
The link with Ratatorsk could be found in the Sandman of Gaiman, but that would be pushing it a little too far (Loki basically pranks Thor, saying he's pregnant, feeding him big amounts of castor oil making his belly full of shit and putting a cork on his ass, and Ratatoskr is the one getting shit on while taking off the cork. Thor says "You're ugly, you're hairy, and you're covered in shit. But you're mine, and I love you!").
I don't see him getting Ragnir all the time though ; more like a captain America thing, where Usopp can use it to help fight Imu with all his braveness and finally get a grip (pun) of his haki by throwing Ragnir.
He's always in a duo with Nami. She already got Zeus. I can completely see them combine their attacks to create something that would definitely link him to Thor.
I also have more of an intuition than Usopp is going to survive (and not be killed at the end of Elbaph like the scalers are thinking) to all that is happening, because he has to tell the tales - the Tontattas already linked Usopp to Norland, and his name is derivative to the famous Esope (confirmed by Oda). I can see him being the new Louis Arnote, since his book "Bragmen" is considered a collection of lies and tales. Usopp would survive everybody to tell what happened during the One Piece (by exaggerating his role, of course!)
Here's to adding a little bit to the theory! Hope you enjoyed it and sorry if this was already pointed at!