Constantius II?

Yep, Constantius II. The standard FEL TEMP REPARATIO soldier-spearing-fallen-horseman design. Mint looks like Sirmium.

"FEL TEMP REPARATIO" expands to "felicium temporum reparatio" and translates to "happy times restored" or, perhaps more liberally, "happy days are here again". The gory scene gives us some indication of what sort of things the Romans had in mind when they reminisced about the "good old days".

It's much easier to identify types on late Roman bronzes, because by that stage the coin designs had fossilized into less than a dozen different types, as opposed to the hundreds of different designs per emperor you might encounter in the earlier Empire.

Romancoin.info, part of the FORVM website, has some good basic information for categorizing these late Roman bronzes.