Gel

Tetris crossed with Pengo! Why hasn't this been done before? Gel on Xbox Live Arcade has got Pengo's sliding and pushing blocks, now in 3d but instead of just matching the special blocks and busting the ice, you've got to get four like colours together to make them dissolve. That's nifty on it's own, but Gel ads combos. The gel blocks don't disappear when you group them, they slowly dissolve. If you can get another same coloured block alongside the gooey mass before it goes pop, it'll dissolve too giving you a combo where the points will climb as you keep adding blocks and the board will clear faster. It takes a mediocre puzzle game up to a fantastic puzzle game, worth trying out for yourself.