Downloaded Galaga Tekken for my phone a few days ago, and it's a fucking blast. Totally free, too.
It's basically just Galaga, but with Tekken characters flying around instead. Each one has a different kind of shot; some are slow but wide, others fast but narrow, while others can hit an enemy and keep going to kill anything behind it.
There are also ways to activate a number of sort of "screen clearing" special weapons which all use old Namco arcade classics for their graphics (further illustrating why I love Namco; they never, ever forget about their classics).
My favorite is, naturally, the Rolling Thunder one, where the classic computer room pops up, and Albatross drops in to kill everyone present.
http://oi59.tinypic.com/2z5m2qo.jpg
I've also seen ones for Pac-Man and Mappy. Not sure if there are others.
Played for a good long while yesterday and got a great high score. Pretty much finished every stage to the point where it had to start over with harder enemies.
http://oi60.tinypic.com/2h3bigk.jpg
Just downloaded galaga tekken...thanks!