1.
The name given, by players of the game CoD4, to the assault rifle mounted grenade launcher do to the fact that it is seen as requiring little skill to use and the fact that it is, in fact, a tube.
Also, the use of said grenade launcher.
(JWilkesBoof kills HonestFive with an M203 grenade)
HonestFive: "Oh come on man don't noobtube!"
See call of duty 4, cod4, war, games, action, grenade launcher, grenade, launcher, noob, tube, noobtube, john wilkes booth, abraham lincoln, five, fps, shooter, stalin, shenanigans, cheap
2.
The nickname of the the Halo or Halo II rocket launcher when used "noobily" by a noob that hogs the rocket launcher(the most powerful weapon in the game) and tends to " camp" but ultimately loses the battle and/or all his dignity and reputation.
"Your noob tactics only encourage us to severely own you in a few seconds and you won't have your stupid noobtube to help you, think fast ya nooblet!"