Velguarder

Velguarder (ベルガーダー) is Sigma's pet dog/wolf. X faces him before facing Sigma himself in Mega Man X. Velguarder's weakness is Shotgun Ice (provided that the Hadouken wasn't acquired earlier). In Mega Man Xtreme 2, Velguarder is the first boss of the final stages.

Velguarder has also a short appearance in the opening scene of Mega Man X5.

In Mega Man X: Command Mission, a downgraded version of Velguarder makes a cameo as a mass-produced robot called Wild Dog. Wild Dogs are common enemies that appear in the Vanallia Desert.

Trivia

 * Velguarder bears a slight resemblance to Treble & Hot Dog.
 * In Mega Man X, if you use the Hadouken just at the exact moment you regain control of X after the intro sequence, it will jump right in front of you as you shoot him point-blank, hitting him and ending the battle.
 * When fighting Velguarder in Mega Man: Maverick Hunter X, the sound effects it makes are uncannily similar to the ones made by Cerebus, from the Resident Evil series, which is another series developed by Capcom.