A number of travel credit cards come with "travel credits," which reimburse you for specific expenses. The Chase Sapphire Reserve, for example, has a $300 annual travel credit; several cards offer credits toward things like airline fees or hotel bookings; and a bunch of cards have a credit for the application fee for TSA PreCheck or Global Entry.
The less restrictive a credit is, the easier it is to redeem. The easiest travel credit to redeem is one that:
Applies to a broad range of expenses. Some credits are very fickle. You may get $200 a year in "airline credit," but it applies only to incidental fees (not airfare) on a single airline that you have to choose ahead of time. A card may offer hundreds of dollars in credit toward travel, but you have to go through the issuer's booking portal, where rates may be more expensive and options more limited. Other credits, however, are broad and open-ended: $300 on any travel expense, $100 toward any airline booking, and so on.
Shows up automatically on your statement. Your issuer's system should be able to recognize qualifying expenses and then apply the credit to them without you having to do anything. If the only way to receive the credit is by calling a phone number or submitting receipts or other documentation, that makes it harder to redeem, which in turn makes it less likely that you'll redeem (and that may be the point).