Someone you meet online in a game (Quake 3, for example) with a name spelt with capitals at random intervals, numbers, multiple colours if possible and an inprobably tough-sounding name. However, what truely makes a kiddie kicker is his real persona - an eleven year old boy from Minneapolis who's trying to avoid doing his homework and focuses his attention on whopping your ass.
This is an onomatopoeia for laughter. Its origin is the Korean onomatopoeia ㅋㅋㅋ, in which ㅋ stands for the "k" sound, like in raspy, stifled laughter. (I'm not sure why it wound up transliterated as "kekeke" rather than just "kkk", though.) Incidentally, the same onomatopoeia also exists in Japanese, written as けけけ.
Hey Dave, did you get in that girlspants the other night?
Yeah, she could suck a golf ball through a garden hose, but her snatch looked like a kicked over trifle!