SKA a go go is only a "gimmick" in the sense that the chart for that song in every Bemani game ever has the exact same ending (see:
YouTube - beatmania 2ndMIX - SKA a go go and also the Pop'n chart has the stupid ending as well)
Aside from that, basically just bag, SAKURA, and various boss songs
I don't consider step patterns to be "gimmicky", only the fact that the song is easy but they did something stupid like make the song very fast/slow and introduce random stops to make it more difficult