More secret medals:
Liberal Animation: Whack the dead rabbit 10 times.
Your Head Essplode!: Eat the mushroom after making it dark (closed eye in the center, spin the dial)
Holy Shhhhh: 5000 points on the loader minigame.
Headless: Once you have all the deaths, go to the skull tree and take the elevator down. Whack the blue robot from the front.
Birdie: Attack the hand that pops out from behind the tree.
I couldn't find the minigame points using basic methods; 5000 is annoying as hell, got to 3000 and clicked the play button through a head...
It helps to go Speedhack ~2.0 as more heads appear, but they disappear faster as well, so you have to have better reflexes the faster you go. Also, be VERY careful around the play button, it sucks to restart after getting tons of points.