Also known as a smiley attack. An emoticon raid is where a user on a forum or im posts loads of emoticons in one post. This annoys people a lot as it causes computers to slow down (especially low-end ones) and you have scroll the page for like 5 minutes to get past the post containing the emoticon raid.
User1: (loads of emoticons)
User2: WTF dude?
User3: He doing an emoticon raid.