It depends on your business model and where your customers are located. Some of the most commonly used processors for digital products and services are Stripe, PayPal, Paddle, Lemon Squeezy, and 2Checkout (Verifone). Each has different fees, supported countries, dispute handling, and compliance requirements.
If you're selling digital goods, I'd pay close attention to chargeback protection, ease of integration, payout times, and whether the processor acts as the merchant of record. It's also worth checking whether they support the countries you operate in.
I'd be interested to hear what others are using and how their experiences have been, especially regarding disputes, account stability, and support.