Interactive Brokers feels like the perfect broker for someone who knows what he's doing. They have a mostly easy-to-use app full of every sort of info you could need, one of the best margin rates around, and letting you trade virtually every asset with any position imaginable. There's not a ton of flashy promotion and there's definitely some cruft logging in or managing settings on the app, but otherwise this is about the perfect broker.
For someone who just wants to make basic trades, Robinhood is honestly a pretty okay option. It definitely has the easiest-to-use interface and flashy modern marketing. Yet beyond those shallow things, it also has a great margin rate, and a rare (small) percentage match on retirement contributions, making this a great place to park your IRAs and effectively contribute a little beyond what you normally could.
A little bit niche, but if you are interested in buying bonds, there's no better place than Public. It makes understanding bonds accessible and allows fractional access to some for those just dipping their toes in. Beyond that, it also supports stock trading with a very easy-to-use interface and also typically ties for best margin rates. It's another strong option, especially for more conservative yet unconventional investors.