You sure can—but there may additional steps. At gas stations, you should be able to pay at the pump. If your transaction can’t be completed, you’ll need to use your card inside the station.
Hotels and car rentals often require a credit card and that’ll mean that they have to put a “hold” on your card—so part of the balance of your gift card may not be available. And, for tipping, the merchant or issuer may decide to authorize your transaction for an additional 20% above your total bill. The amount of your tip is still your choice though.