I use it for everything.

I have unique/monthly limit cards:

  * My kid's swim class has a unique card.
  * Wife's phone (setup before Google started rejecting their cards)
  * Cable bill
  * Netflix
  * Personal AWS bill
  * Gymboree
  * Monthly self-storage

Recently closed one-time cards:

  * Online grocery order
  * Delivery food order (leave some padding for tip)
  * Online clothing retailers
  * Charitable donations paid via CC
  * Tickets to DisneyWorld
  * Every penny that goes through PayPal because I don't trust them for a second

Literally, anything that we pay for over the phone or online.

One place I'm especially happy to have it is my vet. They're really bad at billing. They've double billed me twice. Now I keep a dead card on file (they want a card) and give them a new one with a hard limit every time I have to pay a bill. No more double billing and I can see when they're screwing up.