"Big Daddy" is also the name of one of the more interesting character types in the excellent
FPS BioShock. The character is interesting in that it is a heavily-armed
symbiotic defender of another character class (called a
little sister) that is very tough to kill (she heals almost instantly and has to be killed with direct action) but has no offensive capability.
A Big Daddy is basically a genetically-modified human in a (very) specially tailored diving suit. Instead of a hose leading to a separate air pump there is a huge twin-tank rebreather system that allows the Big Daddy to go anywhere in the underwater city (called Rapture) he and his young defenseless charge live in.
There are two main types of Big Daddy, with standard and elite classes in each. "Bouncers" fight primarily with their "hands" (one being a wicked drill) and "Rosies" have a powerful rivet gun that can punch holes in almost anything. (Rosie the riveter - get it?)
The Bouncers have a bubble-shaped multi-porthole diving helmet with a welded-on tube steel reinforcement cage while the elites have fancier helmets with decorative helmet wings that protect the helmet in a similar manner. Rosies have a helmet with a single center viewing port and small peripheral ports, along with the reinforcing cage on all and decorative wings on the elite's helmets.
Big Daddies have incredible strength, and can move extremely fast when provoked. Rosies also have bombs that they can throw (although they will not hesitate to simply grab you and throw you against something hard).
They are incredibly hard to kill and are actually cyborgs surgically integrated into the suit they wear. They are also chemically tagged with pheremones so they can be easily identified by their tiny defensless partner, who is imprinted to trust and follow anyone looking and smelling like a Big Daddy.
The "little sister" the Big Daddy protects in the decaying city of Rapture has also been genetically modified to provide a home to another symbiont living inside her - a sea slug that can generate raw stem cells. She travels around harvesting genetic material from corpses by drawing blood with a special syringe with a straw on the other end so she can drink it for the slug living inside her. The result (called ADAM) is the currency of the destroyed community, and people are always trying to kill the little sisters to take the slug out of them so they can harvest the ADAM inside.
That's why the little genetic vampires need a big protector. In the game you have to kill the Big Daddy to get your hands on the little girl he protects. (Then it is up to your conscience to decide how badly you need the ADAM she carries.)