What does Halfling Luck work with?

[Harrysonford]

Does the lucky feature from the halfling race work on:
1. Death savings throws?
2. Initiative?
3. Counterspell?

[Specter]

Any d20 you roll.

[Coffee_Dragon]

So you end up rolling for everyone at the table.

[greenstone]

From the PHB: "When you roll a 1 on the d20 for an attack roll, ability check, or saving throw, you can reroll the die and must use the new roll."

So...
1. Death savings throws? ... Yes, it's a Saving Throw.
2. Initiative? ... Yes, it's an Ability Check.
3. Counterspell? .. Yes, it's an Ability Check.