Librarian Dreadnought
Ah yes, the Blood Angels infamous and we mean INFAMOUS Librarian Dreadnought. Potentially debated as one of the most derptastic and bullshittery idea to ever grace the face of Ward, the Librarian Dreadnought ties with the equally infamous Grey Knight Dreadknight and the Centurions in terms of balls-to-the-walls, over-the-top stupidity. Seriously you would think that a baby carrier would top the list, but a psychic quadriplegic in a mech suit shooting warp lightning and even flying is just as rage-inducing to any reasonable members on /tg/.
Overview
The Librarian Dreadnought is a variant of the Furioso Dreadnought design utilized by the Blood Angels. Piloted by crippled and wounded Librarians from the Chapter, Librarian Dreadnoughts are perhaps the most lethal impractical of their kind. They combine the psychic might of a Librarian with the unyielding body and heavy firepower of a Dreadnought. Librarian Dreadnoughts have the ability to call upon the same psyker powers that they and many of their Astartes Librarians would call upon during combat.
The Librarian Dreadnought is equipped with two Fists, one armed with a built-in Storm Bolter and the other equipped with a Dreadnought Force Weapon (Don't ask why or how the Blood Angels manage to get their hands on Force Weapons exclusive to the Grey Knights, then again they somehow found the secrets to make the Baal Predator and Furioso Dreadnought so I guess our pretty little bishonen vampires actually live on a hidden archeo-tech city underground Baal).
The cheesy part here, of course, is the "Librarian" part, or more to the point, the Wings of Sanguinius psychic power. You see, at one point for some reason Librarians didn't have access to Jump Packs. In order to remedy that, Blood Angels Librarians were given a psychic power that (in essence) gave them a Jump Pack for the turn if they successfully called upon it. (They actually manifested wings which might sound a bit retarded, but it's fitting for the Sons of Sanguinius and his whole angel-shtick.) Of course, when used on no-name average Libby so he can accompany his pals into the fray or act a suicide one-man distraction/character killer when combined to a Force Weapon, it was decent. Strong in the right circumstances, but definitely not OP. And then, suddenly, A GODDAMN DREADNOUGHT (you know, the thing that many units simply can't harm in melee thanks to it being a vehicle) CHARACTER (meaning it could attribute its melee attacks and strike those few that could harm him) WITH STRENGTH 10 (Hello, Instant Death!) AND A FORCE WEAPON (even more Instant Death!) could suddenly move twice as fast and ignore terrain... Yeah.
Some people thought it might just be a little too much and expressed their concerns. This... thing's answer was to introduce even more broken stuff into the game. That's GW for you...