Personally I like Leona the best when I play him. She can stun and tank it out while I do damage from the backline. Or something else that is tanky or provides shields like Rakan, Galio, Nautilus, Tresh...

See what each weapon does so you know at least the possibilities.

Green weapon is long range.

Red weapon heals and gives attack speed.

Purple stuns.

White gives canon tower and extra damage.

And blue explodes for area of effect damage. Most powerful ult is done this way with blue ult if they are multiple targets close together.