*in the highschool bathroom*
Person one: "Yo, hit this shit my nigga!"
Person two: "You're such a fucking niccer."
Person one: "fuck you say to me?"
*Fight starts, but the niccer faint due to too much nicotine*
The word "nice" with several appended "e"s includes a degree of "niceness" to the original phrase. It is used in online chats to indicate strength of the usage of the word without using modifiers such as "very" or "quite".
DudeA: "I just finished my homework."
DudeB: "nicee."
In another situation:
DudeA: "I just rooted the NCSA!"
DudeB: "niceeeeeeee!"