My nick "extremely" came about because my domain name is "hostile.org". :) Plus, I have a history of picking adverbs for nicknames since they are much less likely to be picked than nouns, verbs, or adjectives. In the entire list to date per the index the only other nick ending in -ly is tily... so unless there is something "ti" that you can perform something else in the manner of I think I should be safe in asserting that adverbs are rare. :)

These days I mostly use "furtively" or "furt1v3ly". I used furtively as a nick when playing first-person shooters and other online games. That one was picked because my play style is anything but furtive in manner.