I think the Elder Wand is not unbeatable but just very powerful. Voldemort didn't kill Harry, really. If I remember correctly what happened was that the wand refused to kill its true owner and the spell went back and killed Voldemort instead. I remember Harry telling Voldemort to give him back his wand and explaining that Malfoy defeated Dumbledore before Snape killed him, so it was Voldemort the one using the Elder Wand. I think Dumbledore realized that in Goblet of Fire. Harry said that he saw a gleam of triumph in Dumbledore's eyes, but then thought perhaps he had imagined it.
The one of the three Hallows I found most interesting was actually the Stone. Like in an episode of Sabrina the Teenage Witch, when her aunts gave her a reanimation card for Halloween.
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"Of all God's creatures, there is only one that cannot be made slave of the leash. That one is the cat. If man could be crossed with the cat it would improve the man, but it would deteriorate the cat." - Mark Twain