everyone needs to be playing Alien Hominid; regardless if you've played Newground's flash version.
you need to play it. you just do. trust me, i know my poop. and before you say something asinine like "what's that got to do with ANYTHING?", let me remind you that my middle name is Jesus.
so go play it, before i turn all of the water in your body to wine; and you leave this world in the happiest of stupors, and your SO finds your smiling, drool-drenched corpse reeking of old grapes and peasant's feet.
that is to say; it's funny as all heck (evil the cat included), its hard as they come (gradius v comes to mind), and it plays like a true update to Contra or any of the sidescrollin' shooters of yore. and it's two-player simultaneous. (if you haven't noticed, i've got a thing for co-op; which is one of the reasons i never picked up Halo 2)
merry belated christmas.