Shield:
This powerup lasts for 30 seconds, and can protect you from one hit from any bomb. They do not stack, so getting another shield will simply refresh the one you already have. Look for these during those explosion-heavy game modes.
Ninja:
This powerup lasts for 20 seconds, and gives you 5 jumps instead of one. Use this to stay above the danger below, but be careful when it runs out. These can get you out of deadly canyons and over difficult terrain.
Explosion:
This powerup makes you temporarily invincible before you explode, allowing you to reach more powerups or get closer to the bottom. These are useful when you're surrounded, and are crucial for getting to the bottom quickly. Be careful not to get stuck in your newly created death pit. Be warned, these do not stack, and you can only equip one explosive at a time (this includes lane-clears).
Fire:
This powerup lasts for 10 seconds, and lets you burn your way down to other powerups or bomb blocks. Be careful, as you aren't invincible. Use these to clear out small areas or tunnels, or reach nearby powerups to create powerful powerup chains.
Lane-Clear:
This powerup also makes you temporarily invincible before clearing out three layers of the field. Use this to create temporary bomb shelters or reach areas on the other side of the map. Can help you level deadly terrain as well. Be aware, you cannot stack explosives, and these can cancel out any previously equipped explosive powerups.
Time-Slow:
This powerup lasts for 10 seconds, and slows the game, allowing you to think more clearly and act more quickly. The poewrup also can give you some degree of night vision in dark levels.
Rocket:
This powerup instantly blasts you upward through any blocks, and creates a small explosion from your starting position. This powerup can quickly get you out of dangerous situations, but be aware as they can put in you in even more danger if you aren't careful.