In addition to the Heavy's new boxing gloves, cleverly dubbed "Killing Gloves of Boxing" or K.G.B., Valve has announced the Heavy's second unlockable weapon.

Her name is "Natascha," and anyone struck by her bullets will be slowed for an instant, thus severely limiting the target's options when faced with an approaching Heavy Weapons Guy. 

Valve recommends Heavy players use Natascha against fleeing enemies, or as a useful tool when coming around corners to surprise other players, which is about as welcome a surprise as turning the corner to find a Level 3 Sentry pointed at you.

A word of caution, though: check for enemy Heavies wielding Sasha first because Natascha deals less damage than her predecessor:

The Heavy's second unlockable, Natascha, slows enemies with her bullets. Anyone damaged by her will move slower for an instant, encouraging them to find cover or turn and face the Heavy, mano-a-tiny-itty-bitty-mano. Unfortunately, Natascha is slightly weaker than Sasha, so she takes longer to finish off a victim. As a result, Natascha's great against fleeing cowards, such as Scouts & Medics, and less great against anyone actively trying to kill her master. Heavies that like to jump around corners and surprise groups of startled enemy crybabies will also find her very useful, although they should look for a Sasha-wielding enemy Heavy before they leap.

For those who don't remember Sasha, Valve's "Meet the Heavy" video provides a humorous refresher while reminding us exactly why no one likes going one on one with this deceptively friendly individual: