Video games are an easy channel for money launderers;
gift cards are an easy device for money launderers;
crypto-coin exchanges are an easy place for money laundering;
small businesses are easy covers for money laundering;
any cash oriented business like strip clubs are prime targets for money laundering;
PACs and other political gray groups are very easy to launder money through;
churches are very easy to launder money through, without even any taxes;
And oh yeah, fucking international banks.
A lot of things can be used to illegally transfer funds/money launder.