This word can be used as a way to express excitement, agreement, horror, or as an adjective (both positive and negative), an adverb, and even a noun (as a replacement for a swearword.)
"Hey-- guess what! I just got my Linkin Park CD signed by Linkin Park themselves!"
"EEP!!!!"
Kathryn: *sneaks up behind Coral, grabs her ribs*
Coral: Eeeeep!
Kathryn: Haha!
Coral: No fair, you scared me
Kathryn: Yeah, you eeped that said it all *cackles*