Marneus Calgar
Marneus Augustus Calgar (also known as The Notorious M.A.C, The MAC Daddy, Margayness Cockguzzler, Pimp Daddy Calgar, and Papa Smurf) is a character from the fictional Warhammer 40k universe. According to Matt Ward, 5th edition codex writer, Calgar is the spiritual liege of every Space Marine ever. All the Space Marines look up to him and strive ever jovially to be more like him and his Ultramarines, but because of their laughable shortcomings, most Chapters, including the Dark Angels, White Scars, Imperial Fists, Blood Angels, Iron Hands, Salamanders, Raven Guard, Space Wolves and all their successors, will never be as good. It is stressed constantly in the vanilla Space Marine codex and even mentioned a bit in the Blood Angels codex. The entirety of the Imperium awaits the day the Emperor awakes so that the Emperor may proclaim Calgar the rightful heir to the Imperial throne. As a surely irrelevant side note, Matt Ward plays Ultramarines Necrons.
Marneus Calgar is the current Chapter Master of the Ultramarines Chapter of Space Marines, and titled Lord Macragge. Following a skirmish against the Tyranid Hive Fleet Perseus in 976.M41, Calgar lost all four limbs as well as large areas of body tissue and his left eye. Now fitted with bionic replacements, he is more machine than man twisted and evil. Several fa/tg/uys have argued that he currently bears a prosthetic robotic penis .
Calgar is one of the big three, the others being Dante and Logan, the three Chapter Masters the whole Imperium knows. While Dante is worshipped as a larger than life legend and Logan is beloved for being a bro to the common man, Calgar is respected for his leadership, both in battle and ruling Ultramar.
His characteristic weapons are the Gauntlets of Ultramar, which were reclaimed by the Primarch Roboute Guilliman from a Chaos Champion. These gauntlets allow Calgar to bash gaping holes in enemy lines, allowing his men to achieve victory for the Imperium in a joyous slaughter of the heretic forces across the galaxy. They do, however, make it extremely difficult to use restroom facilities, turn door handles, or hold small objects.
An unofficial nickname for Marneus is "Papa Smurf", due to other players referring to the Ultramarines as Smurfs and Calgar being their leader. The nickname has its origin in the actual miniatures' diminutive size and the fact that they are blue. One could also point out of course that the average cartoon smurf is either a total dick or pants-on-head-retarded, and requires Papa Smurf's constant leadership and guidance just to function on an everyday basis. This allows us to extend the metaphor in a hilarious way.
As of 6th edition he is also a xenos-loving bastard, having allowed the Tau to evacuate a planet that was facing Exterminatus due to a Tyranid infestation. To be fair, though, the Tau are one of two races (the other being Eldar) who work with the Imperials at points, so this could be just a bargaining chip to be used later.
He Also duel wield Necron Pylons while the Ultramarines were retaken Danmos (before you ask, Phil Kelly wrote this, surprisingly).
On the Tabletop
Calgar is your typical "cost more than a Land Raider gonna become a lord of war in the seventh edition codex" HQ choice, he's a Chapter Master with Eternal Warrior, the Gauntlets count as two power fists and a storm bolter with AP 2.
But his stats in Combat aren't why he's of use.
Calgar can allow the entire Ultramarine force to choose to pass of fail any moral test they may make. As well as using a Ultramarine combat doctrine twice, as well as rolling the Warlord trait three times and pick the one you want. Allowing him to be one of the most tactically flexible HQs in the Codex.
So while costing a ton he's well worth it for what he does for your army. Trying to build a Chapter Master with similar stats ends up costing around the same as him without the nifty morale shenanigans that Calgar has. Seriously! Taking a Chapter Master with artificer armour, the Shield Eternal and The Burning Blade will build you a character who is better than Calgar in CC due to striking at initiative, a 3++, and blind (along with incandescent), costs 20 points less, however, Calgar has an extra strength point on top of that, better vs vehicles due to his pretty much armour bane rule, and an ap 2 storm bolter. That's not even taking into account the moral rules Calgar gets, the triple warlord trait roll (you pick one from the rolls) and the double doctrine ability (although the chapter master would be able to choose his own chapter tactics, whilst Calgar has the misfortune of being an ultramarine.) So basically Calgar is well worth his salt. Also he can take 3 minimum units of honour guard to troll the fuck outta everyone.