For example, the Bard Magic Secrets feature says:
Choose two spells of any kind.[…] The spells chosen count as bard spells for you.
I am looking for a conclusive list of such characteristics. Note that the Spellcasting function is not included in this, nor are the features that allow you to cast a specific spell a certain number of times for long or short rest.
All official releases.
Motivation: Being able to cast spells like Green-Flame Blade or Eldritch Blast is usually exclusive to only a small selection of classes. A feature that would allow, for example, that a cleric cast these spells could open a lot of new options for the creation of characters that center around such a spell.