This sword has bailed Harry out a couple of times in the course of the series, so we have some strong positive feels about it. If it hadn't appeared to Harry in the Chamber of Secrets, after all, where would we be? And it was super-handy that Snape sent the sword to Harry when he was trying to destroy Horcruxes back in Part 1.
Overall, we're pro-sword.
Unfortunately, some other folks are also very pro-sword, but in a kind of grabby/greedy way. Harry has to promise to give the Sword of Gryffindor to Griphook, a goblin who used to work at Gringotts, in exchange for his help breaking into the bank to find a Horcrux. Griphook ends up taking his payment mid-mission and running off, leaving Harry and the others in serious danger.
That sword was so important to Griphook, he really didn't have the time or inclination to think about anything (or anyone) else. To him, the sword was a prize, not an instrument for quashing out evil (as it is for Harry and the gang).
Karma circles around and nips Griphook in the butt, though. We don't see what happens, but we know he ends up dead on Voldemort's floor, and the sword disappears from his cold, dead hands. It only reappears at the end of the film, when it presents itself to Neville, who then uses it to kill Voldemort's snake.
The takeaway from all this? The sword isn't something that can be owned; it has a whole kind of life and purpose of its own, which mostly involves appearing to/helping out good folks. And for sure, it is not some prize to be won or bartered for.
And Griphook learns this the hard way.