For international payments: Paypal, 2Checkout, Moneybookers, CarrotPay
For domestic payments: Bank Transfer.
Paypal = Must have. Everyone has it. If you don't offer it you cut out a huge segment of the market unless you have some niche/must have product that convinces the buyer of taking the time/effort to use credit card or other payment method.
CarrotPay = Good option for HK based providers, they offer Credit Card only transactions as well as account based payments. Mostly for HKD based transactions though but still usable with other currencies
[Disclaimer: I know the owner of CarrotPay so may be biased. I got my account at WHT banned for recommending them... go figure]
Bank Transfer makes up about 40% of our payments. Operating with bank accounts in 3 countries definitely makes bank transfer easy for our HK, US, and EU clients and it is definitely preferred by us. Never seen a bank transfer reversed so safest is def the best.