Collective consciousness is a concept utilized in many video games, as enemies with a collective mind are common and make for an interesting adversary, provided that the player must kill or destroy the "hub", or "hive", to disable individual foes. Over the years many different approaches to the concept developed, however two of them are ere especially mention-worthy.
Legion, one of commander Shepard's crew in Mass Effect 2 is a geth - a mechanical humanoid AI. The geth operate individually, however, their artificial minds are all linked by a mainframe. That is why Legion refers to himself using the plural pronoun "us". Their operation pattern is exactly that of a computer network: they comunicate with each other to exchange information and make crucial decision, but also each and every unit is able to function individually, whilst being disconnected from the network. Legion operates in this way in the game. Being disconnected from the network means only that there is no information flow between individual units - all units retain their abilities and the awareness of their own existence.
In Planescape: Torment, Rats represent a completely different kind of collective consciousness, than the one presented in Mass Effect. The ordinary street rat by itself is just a rodent, barely posing any threat whatsoever. However, when a group of rats is in the same location, their abilities grow. The more rats, the bigger their power. It is like if the IQ of one being merged with the IQ of another, and another. This way the "collective IQ" piles up, thus creating mind power proportional to the amount of individual minds involved in the merger. For example, one rat will just simply attack a character, three rats are already capable of casting minor spells. A group of rats encountered in the sewers of Sigil can cast a complex spell, like chain lightning. When enough rats gather they form the ultimate collective consciousness form: Many-As-One. This being consists of thousands of rats and has the intellectual abilities of a super human, it can communicate with humans telepathically etc. It also refers to itself using the first person plural pronoun.