The Freeze Banana is a Banana that, when sliced, makes all fruit and bombs flying on and off the screen slow down in their movement for a few seconds. While this banana is active, the time freezes. During this time, if a bomb is hit, you will lose your powerup.
The bonus point achievement "Nothin' but Freeze" requires the player to slice only Freeze bananas out of the three types and it rewards 30 points at the end of the Arcade Mode or Fruit Ninja Frenzy match.
Freeze Bananas, like all the others, are only found in Arcade Mode. You can get the Ice Blade by slicing 20 of these bonuses.
Fruit Ninja Frenzy
In Fruit Ninja Frenzy, there is an achievement row dedicated to Freeze Bananas. Getting gold medals in all of the achievements gives you the Ice Blade.