Yea my top favorite is actually a niche-of-a-niche, trouser filling.
Panties I've been getting into a little more lately, I just don't like that the mess escapes out the holes for the legs so quickly-it's my favorite aspect in jeans getting filled that they catch that mess underneath.
It's pretty damn awesome when panties are filled with the trousers unzipped (and still on) though (well..something I've only seen done two or three times in WAM clip history)
What the world needs now is more girls getting mess poured into their trousers...:-)