E.g. using it as a song title, using these names in my own games, as a bussiness name
I think it matters. Parody is usually okay, but if you took the name of say, Gordon Freeman-- and used a crowbar for your logo as a web design company, you most definitely would get sued it Valve caught wind.
IANAL. Not unless they’re in the public domain. It can depend on how litigious the company happens to be and/or how much attention you get, but eventually they’ll come around and the more successful you get, the more likely they are to come after you. Any company that has intellectual property has a sort of responsibility to protect it, else they run the risk of losing that protection when they may really need it. That’s why I think Nintendo especially is so protective of their IP, they DGAF and will go after anybody, whether it’s for a fan project made out of love or whatever, doesn’t matter, Cease & Desist.
A song title or work of art is probably ok, maybe even a band name (?), but a business name might be stretching it, it just depends on how much you’re leaning into the original work. If you make up a business called ‘Super Mario’s Pipe Cleaners’ and you basically rip off all the imagery from Super Mario games to establish your business, that’s probably not going to go well.
Using it in your own games? Maybe it’d depend on how it’s worked in. If it’s a cookiecutter copy of Princess Peach, then probably copyright infringement, but if it’s a parody or a loose homage to a character, that might stand a better chance. It really just depends on the context.
Song title, probably not. Names covered by a trademark or existing copyright or with an obvious connection to existing IP, probably yes. Especially if you’re making money with it or doing something that can be construed as competition with the trademark or copyright holder. The specifics will depend on the details but its usually not a good idea, or if you do it then be prepared to cease and desist because you will likely get a letter in the mail telling you you’re getting sued if you don’t. If its obvious parody or satire that changes things a bit, or adds further complications and a potential defense you can use if sued.