As far as i can tell shank is a worthless piece of monkey spit. Right now i use him to carry extra mortars but he is so weak its not worth it.
Any ideas or suggestions of what i could use him for?

In my last game I severed his head with a machete and then left him.
I was in a bad mood...
I'd suggest he isn't really worth having around, unless you're desperate.

One fun way to play (for me anyway) is to try a run through the game without hiring any mercs. So first I get ira and dimitri. Then I head down to tixa with those three, and after a very difficult fight, spring shank and dynamo. If you use any character enough they get passable with firearms. You can use him to hide around a corner, and shoot them as they come round.
Otherwise, a mule is just about all he's good for.

After he gets you the new refuel point for the helicopter he's not much use unless you keep him as part of a salvage squad like I do. I use some of the more expensive mercs so need to keep a tight watch income and have him and some other cheap/free troops ferry stuff to sell guns/pelts/armour etc at the three buyers. With him and Mad-dog busy on permanent repair duty I never have to waste my top team on non combat activities.

That is a pretty good idea for using him and Maddog as "go-fer's".

Dont you escort him somewhere to talk to somebody (I think the name was Jack, cant remember) to get a deal on buying gas?? Not sure if he left the group afterwards. I never use any of the Arulco recruits except for, the rebels, doc whatshisname, and the robot.

Funny...for a second I thought you were talking about SHANK - the videogame...

Having Shank let's you buy gas in Estoni. He doesn't have to be in Estoni to be able to buy gas but I'm not sure if you can still buy gas if you fire him. Then again, he's cheap so you might as well keep him around for the convenience of being able to buy gas.

Yes you can still buy gas even if you dismiss him. My current play-through I got him to talk to the junk yard owner who then has gas cans for sale and I fired Shank after that. I was nice enough to heal him and Dynamo first although by nice I mean get extra practice for my medics.

He actually led a charmed life in a previous game as time and again he was lucky enough to walk out enemy traps when I was using him as cannon fodder. He ran into a building and got interrupted by a red-shirt who went for a knife kill only for him to get interrupted by Sidney. Sid spun him around with a shot to the head and the grey-shirt with the rocket rifle who was the levels other only surviving enemy shot him in the chest by mistake with a rocket rifle. Then she sat out of points six feet away from Shank who was carrying a fully loaded CAWs and even he can't miss at that range. Shank's secret skill may be ridiculously good luck.