"What, now?" and "Who did what, now?" are both Snizzisms that I've gotten into the habit of using regularly, and even been able to my friends that don't even come here to use them.

Also, "Schooled!" "Smoked!" "You got served!" or the reverse of "We/I just got schooled." and so forth are ones I use. The served one is usually used sarcastically because that was the most retarded idea for a <a href="http://www.allmovie.com/cg/avg.dll?p=avg&sql=1:286929">movie</a> ever.