Never quite done them before, but got a few to do. For now, they are for different strengths of air to ground collisions, and the last is a death animation.
For medium landings (from jump) [Changed in edit 1: less gravity]
For light landings- being knocked back
For heavy landings (fatal). I feel it is way too strong, and if I use it, it will probably be for a desert fatality. Gravity too strong, may use for water impact.
Based off of the above. Forgot to change the eye-white transparency. From Idle animation.
For lighter landings [added in edit 1]
A medium-heavy landing effect, testing dispersing the particles (used cheap transparency). I'm not too pleased with it, but the dispersion looks better. [added in edit 1]
A moderate effect from an attack, seems like a bit of an over kill again. [added in edit 2]
Posted in the order in which I made them. I used the transparency on the first for the dithering, and I do feel guilty about it.
Character, from falling animation. Basically a water balloon.

As these aren't too complex (aside from the pop), I plan to have one for many surfaces and collision levels. I have many more on my to-do list, as I'd like for there to be an effect for every action.
These are all one color for now, and I have no idea how to improve them. My stuff always looks great to me until I know what's wrong, and then like not so. I've seen some really neat pixel art effects, mainly explosions.