1. Frodo has an adventurous nature at the beginning of the trilogy, which is unusual for a hobbit. Samwise does not have an adventurous nature, but he goes with Frodo anyway, thereby already doing something he doesn't want to do. This trend then continues throughout the novel. Admittedly, Sam wanted to see the elves. But once he's seen an elf he still agrees to go to Mordor when he could just go home and marry Rosie Cotton. But no - off to Mordor. Bleuch.
2. And Frodo doesn't even want him to go to Mordor, which makes it even braver. Samwise nearly drowns trying to persuade Frodo to take him along. And Frodo looks in two minds about rescuing Sam, for which I can never forgive him. Horrible hobbit.
3. Sam knows Gollum is bad news and puts up with Frodo doubting him and eventually telling him to get lost. Then Sam single-handedly takes on the scariest evil creature of all Middle Earth to save Frodo, even though Frodo told him to nick off.
4. At this point Sam carries the ring himself and at no point does he moan about not being able to remember the taste of strawberries.
5. And when Frodo gives up like the little hairy nerk he is, Sam carries Frodo up the slopes of Mount Doom. Even though he's let Frodo eat all the lembas bread and drink all the water. So he's doing it without the aid of sustenance. And he carried the ring earlier too. Did I mention that?
6. So at Mount Doom Frodo decides to keep the ring. And Sam doesn't just push him in the lava and go home himself. I know I would have.
7. To top it all, after the whole thing is over, Frodo diminishes into the West with the elves for an easy eternity, while Sam stays, has kids, becomes Mayor for a seven consecutive seven year terms, then buries his beloved Rosie and only then takes a boat to the West. And I bet throughout that time he kept his garden beautifully.
Apparently Tolkien recognised that Samwise was the true hero of the novel, and in a private letter compared Sam to the English soldier during World War One, working so hard, so thanklessly, for those that he considers to be his betters. Tolkien saw this self-effacing bravery as the best characteristic of humanity.
For me, Samwise is the best thing about the Lord of the Ringstrilogy. Possibly this is because I do find Frodo to be a bit on the annoying side. I don't think I'm alone in this, am I?