Just for future reference:
Convert the ISO image
hdiutil convert -format UDRW -o newimage.img image.iso
Make the USB stick bootable
sudo fdisk /dev/disk2
flag 1
write
quit
Flash the image to the USB stick
sudo echo
dd bs=1m if=newimage.img | pv -trab | sudo dd bs=1m of=/dev/DISK-DEVICE
DISK-DEVICE will probably be rdisk2
Eject disk
sudo diskutil eject /dev/diskN
See How to create a bootable USB stick on OS X for more information.