This is just a cool little riff i found for a ska song, feel free to use it. 
Riff 1
G|99--9-12-12?5-5---5-9-9-------_
D|99--9-12-12?5-5---5-9-9-------_
A|--------------------------------- _
E|----------------------------------_ 
Riff 2
G|--------------------------------------------
D|9-9-7-7-12-12-10-10h9-------------/17
A|9-9-7-8-12-12-10-10-------------------
E|--------------------------------------------
Order
Riff 1x4
Riff 2x1
Riff 1xAny amount and repeat infinitly
Oh and in the first riff try taking out the last 5 for alittle different sound