Paintbrush

The Paintbrush is the main weapon of Stick Michael. Inspired by the fact that Stick Michael is an artist, he uses it both in the game and Slush Tile Rush. However, it does supposedly make a cameo at the end of the movie when Stick Michael (Gildedguy) is introduced as the creator of the animation.

Slush Invaders (movie)
The paintbrush presumably makes an appearance at the end of the animation when Stick Michael is introduced.

Slush Invaders: Game
In the game, Stick Michael uses his paintbrush to draw these horizontal lines that catch Big Blue to trap him. When Extra Ink is unlocked, the paintbrush's brush line can last for a second longer. TranpoLine allows Stick Michael to use his paintbrush to continue bouncing on a higher height. The paintbrush possibly turns into a sword when Stick Michael uses his Ultra Attack against Big Blue and stays in his golden state for the rest of the level.

Slush Tile Rush
When Stick Michael makes a return in the game, so does his stylus. When Stick Michael is first used, his paintbrush deals weak damage of about 1 every attack. His paintbrush perhaps transforms into a sword when 3-4 Stick Michael tiles are swiped in a row, turning Stick Michael into Gildedguy. When that happens, he deals 20 damage every attack using his sword for 5 turns and for the rest of the goal of beating the enemy.

Trivia

 * Stick Michael's paintbrush is also known as a stylus.