alright, 1st is 1st
an underground game is a game not well known but somewhat famou and players stay in groups, kinda like pivot people. my fave underground games are
X-com enforcer(super rare)
Jet set radio future, this game is epic. i would love to know if anyone plays this
Onimusha Epic series. period. but not really underground, it is broderline-ish
Timesplitters FP this is the only good game of the series but it is funny, gory, fast paced, and awesome
and lastly Star wars Republic commando

if you wanna find out about them click the below links
http://en.wikipedia.com/wiki/Onimusha_(series)/
http://en.wikipedia.com/wiki/Star_Wars_republic_commando
http://en.wikipedia.com/wiki/Jet_set_radio_future
http://en.wikipedia.org/wiki/Timesplitters_Future_Perfect
http://en.wikipedia.org/wiki/X-COM:_Enforcer