Feats of Strength achievements represent the past glories of Azeroth, and as such, they are very difficult — if not impossible — to earn. They are worth no points, and unlike normal achievements, unearned feats are not displayed in the achievements interface. Feats include old-world Player vs. Player ranks, obtaining raremounts, special titles, and more. Feats of Strength achievements are awarded retroactively (that is, they are immediately granted to your character if you qualify) since many of them are impossible to earn in Wrath of the Lich King.
It is great to be able to see your own achievements — but it is even better to let the world know what you have accomplished. By right-clicking other players and selecting the appropriate option, you can compare your achievements to theirs. Every time you earn a new achievement, your accomplishment is announced to your guild and everyone in your immediate vicinity — and the custom achievement animation and sound effect are unmistakable. Also, your achievements are viewable in The Armory allowing you to track and show off your accomplishments via the web.
Warning: The following Sub-Categories are not used in the game but are used by WoWWiki to better organize the pages for your ease in finding the Achievements you are looking for.