I have been a general practitioner thoughout my creative time. Working in technical art (in several genres), fine art / illustration commissions, book covers, and 3D visual mock ups, and in the past front end graphics and coding for web, and some 2D animation. Below is a list of some of the companies I have done work for in the following capacities: As an employee for a company, as a contractor, or subcontractor, as a freelancer - in no particular order:

Ultratech International - freelancer
Wal Mart - sub contract freelancer
Intelligent Automation Inc. - freelancer
Shell Oil - sub contractor freelancer
Com Ed - sub contractor freelancer
Ford Motors - employee of illustration company and contracted freelancer
Shiloh, Delphi, Takata, Johnson Controls - employee of illustration company
Fleet Crew (specialty mining vehicles AU) - sub contracted freelancer
Fox Pro Racing - contracted freelancer
Sun FX (tanning products) - sub contracted freelancer
DARPA - sub contracted freelancer
MAPDE - sub contracted freelancer
HydroDot (medical)- contracted freelancer
Sakana (fishing equipment JA) - sub contracted freelancer
General Plastics - freelancer
Wasatch Microfluidics - freelancer
Stem Tech - freelancer
Microsoft - contract worker
North Dakota State University - freelancer
JWC Environmental / IPEC - freelance
RADAR Engineers - sub contracted freelancer
EZ-RED (specialty auto tools) - freelance
US Trenchless - freelance

Many many more smaller companies, individuals, a few clubs, organizations and charities, in a freelance capacity.