Sparky

 Sparky, or Shakey as it is known in Mega Man Battle Network 5, is a virus from the Mega Man Battle Network series. This virus zigzags down the field at super speeds, so it is incredibly hard to target. When they encounter an obstacle in the middle row, they circle around it a couple of times before zigzagging again. They damage the target upon contact. Variants move faster and idle less as they level up.

Sparky
 Sparkys are green and yellow.

Sparky2/Sparkler
 Sparklers are purple and blue.

Sparky3/Sparknoid
 Sparknoids are orange, blue and green.

Shakey
 Shakeys are green and yellow. They bear the same resemblance as Sparky. However, they are only in Mega Man Battle Network 5.

ShakeyEX
 ShakeyEXs are hot pink and green. They appear in Mega Man Battle Network 5.

Shakey2
 Shakey2s are purple and blue. They bear the same resemblance as Sparkler. However, they are only in Mega Man Battle Network 5.

Shakey2EX
 Shakey2EXs are gray and light-blue. They appear in Mega Man Battle Network 5.

Shakey3
 Shakey3s are orange, blue and green. They bear the same resemblance as Sparknoid. However, they are only in Mega Man Battle Network 5.

Shakey3EX
 Shakey3EXs are black and purple. They appear in Mega Man Battle Network 5.

Source
Sprite images found at Sprites INC