Fellow Craft, the second degree of Freemasonry.

Fuel cell, an electrochemical energy conversion device.

American terrorist Theodore Kaczynski, also known as the Unabomber, who used the signature FC (for "Freedom Club")

Flying Circus, for Monty Python's Flying Circus.

Full Combo, popular term in rhythm-based games like Guitar Hero - meaning not missing a note/beat.

Fooly Cooly, a popular anime show in Japan.

"FC" is the IATA code for Finncomm Airlines

Foot-candle, a unit of brightness.

The "FC" type optical fiber connector

FC, a British progressive rock band formerly known as Final Conflict

Fan club

Football club

Fucked Company, a web site

In biology, the Fc region is a region of an antibody which is constant and binds to receptors

Facilitated communication, an augmentative and alternative communication (AAC) technique

Fedora Core, a Linux distribution

Fibre Channel, a serial computer bus intended for connecting high-speed storage devices to computers

Microsoft File Compare, a software utility shipped with MS-DOS and Microsoft Windows that is a variant of diff

The second generation of the Mazda RX-7 (1986–1991), after the beginning of its vehicle identification number (JM1FC3)

Nintendo's Family Computer, also called "Famicom", the Japanese version of the Nintendo Entertainment System

Friend Code, for Nintendo DS games capable of online play