Phantom Breaker: Battle Grounds was a decently enjoyable sidescrolling beat-'em-up released on Xbox Live Arcade early last year. It's now coming to PS Vita, where it will hopefully gain more visibility, on July 29, 2014. Good game-platform fit! It's priced at $12.
Battle Grounds is a spinoff of 5pb's fighting game Phantom Breaker and features characters from that title -- plus Steins;Gate's Kurisu Makise, as DLC ($6 on PS Vita) -- but you don't have to know anything about its source material to have a good time. Again, "beat-'em-up."