5 Scouts in a storm with powerfist (with shotgun), meltabombs and bolt pistol/CCW
That gives you up to a 44" charge range if you go first (scout turbo boost, 12" move, 2" disembark, 6" assault) with 12 S4 attacks and 3 S8 powerfist attacks plus 6 S4 shots. Not only is that a pretty nasty assault force but its also pretty good at killing enemy vehicles before they have moved (if they are isolated on a flank then its even better as normally its a 'fire and forget' unit that is on a suicide run).
Ofc there is always the fcat that they are a scoring unit that can move 24" a turn, so if you dont see an opportunity to use them as a strike force you can either leave them in reserve (mebbe DS) or just scout behind cover- I would always set my storm up as near the centre of the board as I could get and then use the scout move to put in in an offensive/defensive position, I was doing this with the old SW codex so my storm had a meltagun in it (and a multimelta on it) and everyone with metlabombs so I was using it as a strike anti-tank unit (land raider... what land raider?) but they were certainly a decent assault unit if needed be.