For a set of achievements that tend to be insanely difficult and reward no points, Feats of Strength are still a pretty compelling bunch. In a way, they could be described as a character's history, because they're usually about stuff that you can't do within the game anymore. Owning one of the classic game's original 100% mounts, old PvP mounts like the Vengeful Nether Drake, or 1,000 Stone Keeper's Shards are all signs that your character's been around the block a few times. However, there are still a few -- a very few! -- feats of strength that you can get right now.
I visited this subject in 2009, and a lot's changed since then. Unsurprisingly, a lot of the feats described in that article are no longer attainable (bye-bye, Swift Zulian Tiger!), but a few more have been added.
Fair warning: Most of the Feats of Strength that you can add to a character's collection are either RNG-dependent or grind-intensive to get, and a few featured in our 25 most evil achievements series.