NationStates

Is not a company but is the the most known trademark is Futbol Club Barcelona.
Probably SCAT SA, The main car maker, but is Owned by Volkswagen Group or Grifols.

The Tourist industry of course!

Most likely Panopticorp, it is well known for its creation of the PanPhone - the most popular cellphone in the ASR. Their reach makes them practically a branch of the Reblian Government. Sure, Great Dictator Marco Matiz HAS the power to stop them, but where else is he going to get the new PanPhone X?

Resucejisjegala is Ahakista's national oil and natural gas company which has been instrumental in extracting the nation's fuel resources. The profits from the sales have been instrumental to the nation's long-term investment in its growth and development.

Removed for retcon purposes (2019-08-01)

Fostoria's most famous company is Metakorp, a mining and metallurgy corporation that has a monopoly over its industries. Another thing that has added to their fame is their high wages for workers, plus the amount of cheap raw metal products they have made available.

An honorable mention is Daiychaz Albeihrkorp, made famous for their production of Daiychaz Ale (the county's most popular beverage) and several other beers, soda pops, and the like.

There isn't really any companies, as all services and products are provided by the state. However, some foreign companies are allowed in Viksberg under strict government supervision and regulation. The most famous of these is McDonald's

MSR's Famous company is the TARA Aviation, due that the airline is a budget carrier and it gets most of the tourists, people and cargo inside, outside and around the country at an affordable price.
However, the airline operates primarily on Soviet Built Aircraft. So it became famous on civil enthusiasts.
The airline cannot fly to EU but it flies regularly on MSR's neighbouring countries.

The Airline Operates at least 140+ aircraft, carried 44 million passengers and profited more than USD 5.9 Billion per year.

Arguably the most recognizable company is Coca-Cola. Founded 3 centuries ago in 1892, the company is still going strong from it's headquarters in the Atlanta district of the Dixie megalopolis. The company is seen worldwide as a symbol of Carenian consumerism and it's logo still remains highly recognizable around the globe.

Finland's most famous company is communications, information technology and consumer electronics company Nokia, that recently made it's comeback into smartphone industry.

Charybdis Heavy Industries, even before it became a Pirate world, is one of the Pirate's main arms contractors. They have no qualms in supplying arms so long as the Space Pirates keep their shipments and headquarters secured.

Mercedes Benz.

Bantuardhi's most famous company is Rabbit, an technology company that designs, develops, and sells consumer electronics, computer software, and online services.

Really hard to say, but some of the highlights are:

Ryshun Messerschmidt S.A.F.
Karpeche Vickers S.M.C.
BMW S.O.C.M.
Spitfire S.O.C.M.
Quick recap:

S.A.F = State Air Fleet.
S.M.C = State Munitions Company.
S.O.C.M = State-Owned Car Manufacturer.

Well, it’s probably going to be the Luna Arms Corp., a prominent weapons designer and seller, or the Golden Star Merchant Line, a shipping company responsible for around an entire 18% of the country’s GDP when Exodia first declared independence.

The state-owned information technology company Drexlos Industries is Polyspastonia’s most famous company, notable for producing the cutting-edge Drexsoft commlinks and computers which are available worldwide.

The Litan imperiums prides itself in it's PMC and security industries. The largest company is a tie between Verek Tactical Solutions and Vigil Policing Services. The former having put down numerous armed insurgencies, rebellions, and guerilla group. And the latter lowering crime rates in many cities by as much as 67%.

Kraft Mac 'n Cheese

just kidding, it's Macaroni And Cheese Company as the most famous company

The most famous company in Lexusland would be IRISE, a tech company.

There are three qualifiers in my nation:
-Corona S.L (automobiles)
-Margarita S.L (alcoholic drinks)
-Rapidás S.L (tech)

Glossary:
-S.L: Sociedad Limitada (limited company)

The most famous company is the Underwater Salvage and Recycling Cooperative.

Probably GalacTECH, which markets tech products such as smartphones (NovaPhone), tablets (AuroraTab), laptops (Pulsar), desktops (Quasar), home automation (Vega), smart TVs (CometVision), and game consoles (GammaPlay).

Probably Ko-oren Transit Solutions, the company behind public transport in Ko-oren. Internationally, it might be either Maethoru football club or any of our sports associations.

CPI Pharma, a government-run company that produces just about every medicine and drug under the sun, from upset stomach tablets to powerful painkillers. CPI Pharma is one of the main sources of our wealth, and many countries purchase CPI's pharmaceuticals. However, because of some of the drugs CPI produces, they can be controversial in other countries. Nevertheless, 97% of all medications sold on our own Island are from CPI Pharma.

As far as industries, tourism would take the cake. However, tourism does not have large, organized corporations the way "big pharma" does.