Things is a premium Apple-ecosystem task manager from Cultured Code in Germany; Things 3 won the Apple Design Award in 2017, sells for about $49.99 one-time on macOS and is known for GTD hierarchy and minimal design.
Affinity is Serif's one-time-purchase professional creative suite with Designer, Photo and Publisher apps, priced at about $69.99 each, known for hardware acceleration and Adobe file compatibility.
SendFox is a low-cost email marketing tool founded in the United States in 2019 and owned by AppSumo, offering unlimited sends, landing pages, and automation sequences with a one-time purchase model for content creators.