Knowledge Skills are fairly free-form and open-ended. However, for purposes of inspiration and edification, a list of Knowledge Skills and their known Specializations that have appeared in various books:

20th Century Comic Books

Alcohol

Anthropology

Application Design

Archaeology

Area Knowledge

Arms Dealers

Art

Artificial Intelligence

Astrology (Chinese) (Mayan) (Native American) (Vedic) (Western)

Atlantis Research

Automated Factory Familiarity

BTL Dealers

BTL Production

Biology

Biotechnology

Black IC Design

Body Armor Fabrication

Botany

Bushido Philosophy

Cellular Network Familiarity

Chat Room Familiarity

Chat Rooms

Cheap Synthahol Guzzling

Chemistry (Pharmeceuticals)

Chokepoint Familiarity

Chop Shops

Civil Engineering (Commercial Construction) (Excavation) (Home Construction) (Industrial Construction) (Tunneling)

Combat Biking

Communications Satellite Familiarity

Computer Background

Conspiracy Theories

Cooking

Corporate Finances

Corporate Hosts

Corporate Politics

Corporate Program Designers

Corporate Rumors

Criminal Organizations

Current Events

Cyberdecks

Cybertechnology

Cyberterminal Code Design

Cyberterminal Design

Data Archive Familiarity

Data Brokerage

Data Havens

Data Tracing

Databases

Decker Tricks

Deckmeisters

Defensive Utility Design

Demolitions Background

Desert Wars

Dowsing (Bobber) (Compass) (L-Rod) (Pendulum) (Y-Rod)

Dragons

Drugs

Ecology (Sewers)

Economics

Electronics Background

Elven Society

Elven Wines

Engineering

Esoteric Trivia

Fences

Flatvid Movies

Forensics

Frame Core Design

Fringe Cults

Gambling Card Games

Game Host Familiarity

Gang Identification (Go-Gangs)

Gang Turf

Gear Value

Geology

Gray IC Design

Gunsmithing

Hardcore Punk Bands

History

Humanis Policlub

IC Construct Design

IC Profiles

Iconography

Jackpoint Locations

Japanese Culture

Japanese Society

LTG Familiarity

Legendary Deckers

Legendary Martial Artists

Literature

Local Landmarks

Local Politics

Local Rumor Mill

Lone Star Tactics

Mafia Finances

Mafia Politics

Mafia-Controlled Establishments

Magic Background

Magical Goods Value

Magical Groups

Magical Threats

Matrix Bank Familiarity

Matrix Gangs

Matrix Programs

Matrix Security Procedures

Matrix Topography

Mechanical Traps

Medicine (Pathology) (Toxicology) (Traumatology)

Meditation

Megacorporate Policies

Megacorporate Politics

Megacorporate Research

Megacorporate Security

Mercenary Groups

Mercenary Hot Spots

Metahumanity

Metallurgy

Metalworking

Microchips

Military Winged Aircraft

Miltech Manufacturers

Modern Art

Modern Jazz

Music

NAN Border Patrol Tactics

Named Spirits

Offensive Utility Design

Opera

Operational Utility Design

Parabotany

Paranormal Animals (Urban)

Parapsychology

Parazoology

Philosophy

Physics (Ballistics)

Pirate Trid Broadcasters

Poetry

Police Procedures

Politics

Professional Bodyguarding

Programming Suite Design

Prostitution Rings

Psychology

RTG Familiarity

Redmond Barrens

Roleplaying Games of the Late 20th Century

Rumor Mill

SWAT Team Tactics

Safehouse Locations

Satellite Networks

Sci-Fi Simchips

Scrounging

Sculpture

Seattle Corporate Hosts

Seattle High Society

Seattle Junkyards

Seattle LTG

Seattle Ork Underground

Security Companies

Security Design (Closed Circuit Simsense) (Corporate) (Magical) (Matrix) (Military) (Physical) (Private Home)

Security Network Familiarity

Security Procedures (Government) (Military)

Seedy Ork Bars

Shadowrunner Haunts

Shadowrunner Teams

Sim Starlets

Small Unit Tactics (Vehicle Tactics)

Smuggler Havens

Smuggler Routes

Sociology

Special Utility Design

Spell Design

Street Rumors

Talismongering (Gathering)

Tir Tairngire Politics

Toxic Hazards

Trace IC Design

Tracking

Troll Thrash Metal Bands

Triad Politics

Tribal Lore

Tribal Politics

Underworld Finance

Underworld Politics

Urban Brawl

Virtual Meeting Spots

Weapon Acquisition

Weightlifting

White IC Design

Woodworking

Worm Design

Yakuza Territory

Zoology (Wilderness)

