It's no surprise that George R. R. Martin has taken a lot of inspiration from J.R.R. Tolkien, seeing as Tolkien is considered the father of the fantasy genre. While parallels can easily be drawn between Westeros of Game of Thrones and Middle-Earth, the setting of The Lord of the Rings Franchise, one of the most prominent is between the characters of Martin's Samwell Tarly and Tolkien's Samwise Gamgee.
The unfortunate obvious similarity is that both characters are known for being overweight. From the second Samwell set a foot in Castle Black, he was berated by the other brothers of the Night's Watch. And Sam, well Gollum wasn't afraid to hold back when he called Sam a "stupid, fat hobbit". He was often referred to by the slimy ring-enthusiast as "the fat one", as was Sam by his surroundings at Castle Black.
Yes, they are both named Sam, but even their full names are near-identical. Samwise and Samwell, Gamgee and Tarly, you can tell that Martin wanted us to see the similarities. Not to mention Samwell is often referred to as "Samwell the craven" while Samwise is called "Samwise the brave". I don't think the parallels between the names could be any more obvious.
A True Romantic
When Frodo and Sam were laying on the side of Mount Doom after destroying the One Ring, Frodo, like any other hobbit, was thinking about the Shire. However, Sam had something (or rather someone) more specific: Rosie. As soon as he returned to the Shire, he married her and had little hobbit-babies.
Samwell has the very same devotion to love. No matter what happens, whether it is a White Walker attack or an invasion by the wildlings, Sam always thought first of protecting Gilly. If he had to sacrifice himself to save Gilly and her baby, I'm sure he would do so without a second thought, as Samwise would do for Rosie.
With all the major characters in Game of Thrones, Jon Snow is closest that we have to the Frodo of the story. During the petty squabbles over the Iron Throne, Jon has been bust protecting the entire realm from the White Walkers. If that doesn't make him the main character I don't know what does.
If you haven't noticed, Jon and Frodo never are alone. They always have their best friend to watch their back, give them advice, and basically provide motivation for the hero to complete destiny. Without either of the Sams, Westeros and Middle-Earth alike would probably be in ruins.
At first glance, both Sams seem like the type to turn and run from danger. They aren't as obviously heroic as the other characters in the stories, but when danger looks them in the face, they are just as brave, if not more brave, than any other character you can think of.
When a White Walker was stumbling up on Samwell and Gilly, Sam stood his ground and protected them by killing the Walker with dragonglass. And when Frodo was defeated by the massive spider Shelob, Sam charged in and killed it to save his friend. Both characters show an extraordinary amount amount of bravery to save those around them.