There should be more abilities like Kalista's R
Here are some ideas
Blitzcrank's grab can pull allies (Think of the blitz flash Ult grab amumu, Amumu ult wombo combo)
Nautilus's hook can pull ally closer together, and reduces the cooldown (similar to hooking a wall)
Singed's Throw can throw allies (Can get a carry out of trouble if out out of position)
Alistar's W can headbutt allies away (most likely a bad idea, but cool regardless)
Get the idea...(These idea's are meant to give tanks some hidden utility and require more skill than, hey I'm a wall, try to get by me)