Spark Shock

Spark Shock (スパークショック) is Spark Man's special weapon. This weapon basically shoots sparks, as the name implies. Some enemies merely get paralyzed when hit, but a few enemies like Magnet Man can be damaged by this weapon. It's downside is only two enemies can be stunned at a time and you cannot change your weapon while there's one stunned.

Capacity
Spark Shock uses one weapon energy unit in Mega Man 3 and Mega Man III. With a full weapon energy gauge, it can be used 28 times in Mega Man 3 and 19 times in Mega Man III.

Bosses weak against Spark Shock

 * Mega Man 3: Magnet Man, Doc Robot (Air Man and Bubble Man), Spark Man (2nd Encounter), Wily Machine No. 3 (1st Form)
 * Mega Man III: Snake Man, Giant Suzy
 * Mega Man: The Wily Wars: Iron Ball, Wily Machine (1st Form)
 * Super Adventure Rockman: Ra Thor

Bosses immune to Spark Shock

 * Mega Man 3: Needle Man, Hard Man, Doc Robot (Flash Man), Yellow Devil Mark 2, Holograph Mega Men, Gamma
 * Mega Man III: Dive Man, Drill Man, Skull Man, Punk, Wily Machine
 * Mega Man: The Wily Wars: Buster Rod. G, Wily Machine (2st Form)

Other media
Mega Man uses the Spark Shock and Gyro Attack at the same time in episode 8 of the Mega Man animated series. When obtaining the weapon, an electrode can be seen in its design, probably for firing the sparks.