The following boosts are available.

Glacier
Same effect as the Glacier power-up, without having to match five gems first.

Ice Pick
Eliminate one gem anywhere on the level.

Snowball
Have five extra moves.

Torch
Eliminate any eight connected gems.

Save boosts as a last resort, until they are absolutely needed. Each character has different boosts. Switch characters to get the most useful boosts for the level you are playing.