Bilbo/Dwalin. For reasons.
Fake dating: By the time they reach Beron’s house, suddenly all the dwarves start treating Bilbo differently because he’s a hero now after saving Thorin. Bilbo is unused to all of this attention and he’s uncomfortable about everyone hitting on him. Except, Dwalin is the only one who hasn’t treated him differently so when some of the dwarves corner Bilbo and kinda demand a reason why he won’t take any of their offers, Bilbo nervously says the first thing he can thing of which is that he’s dating Dwalin. Dwalin goes along with it because he remembers how much attention he first got when he had become a hero. Eventually though, the dating act becomes real when the first thing Dwalin does after being released from his barrel is kiss Bilbo in front of the company.
Bodyswap: They’re pretty sure it had something to do with that fruit they found in the woods but only shared with one another and no one else in the company. Dwalin doesn’t want to go to Gandalf right away because he thinks it will wear off on its own in a few days. Bilbo just hopes that no one notices. Though he does think it’s rather nice to keep his hand pressed against Dwalin’s hard abs at all times.
Sexpollen/fuck or die/aliens made them do it: Bilbo is wandering through Beron’s garden and stumbles upon an odd flower. Dwalin was ordered to fetch the hobbit for lunch only to find a horny hobbit in the garden that instantly jumps him. Dwalin had always enjoyed a nooner.
Dark!fic: While on the road, during his watch, Dwalin would climb into Bilbo’s bedroll and force himself onto the hobbit. He always threatened that Bilbo needed to keep quiet because if any of the others found out that he was such a good lay then Dwalin would have to take turns. Fearing that the others in the company would also hurt him, Bilbo keeps quiet about the almost nightly rape and slowly becomes more closed off from the others. The entire company dies before they even get near to Erebor.
Secret kinks: Bilbo has always appreciated art and Dwalin’s tattoos are art in their own way. Dwalin, on the other hand, has a size difference kink and loves watching Bilbo’s little hands on his body.
Their first kiss: Dwalin had been pining for Bilbo the entire journey and vice versa. After BoFtA, Bilbo comes out of Thorin’s tent and tugs on Dwalin’s beard to finally go for it.
Meeting the parents: Most don’t know that Dwalin’s mother is still alive, she’s smaller than Balin but still just as fierce as Dwalin. She absolutely loves Bilbo when he invites her for tea and makes three different types of cookies. Turns out, Dwalin got his fierceness and sweet tooth from his mother.
Moving in together: Dwalin can’t stay in the mountain since it doesn’t feel right without Thorin as the king. Bilbo invites him back to live in the Shire with him since Bilbo can’t imagine such a quiet life anymore. Slowly, the two find peace within one another.
A crossover of my choice: Dwalin as Batman and Bilbo as Catwoman. I’m really not good with crossovers?
An au of my choice: Gangsters. Dwalin is the right hand of mob boss Thorin and he’s in charge of guarding the little thief they caught. Unfortunately, the thief is actually pretty charming. Dwalin really doesn’t want to have to hurt the fellow and when Thorin finally announces that they want to hire Bilbo instead of send him to the cleaners Dwalin lets out a huge breath of relief.
Another trope/scenario: De-aged. Bilbo somehow is de-aged and little Bilbo favors Dwalin the most surprisingly. He loves to climb all over the other dwarf and he won’t take naps unless Dwalin lays down with him. He also likes to kiss Dwalin’s bald head every time the dwarf puts Bilbo on his shoulders for a ride.