*not for use with zombies
You can, however, set it on fire with an Incendio spell. While this particular charm can be very effective against a horde of undead, it can also backfire on you, and therefore should be used only with the greatest caution. A flaming zombie will still be able to move for a time, and it won't stop chasing you until it's brain is consumed by the fire. Meanwhile, it
|Fire! Fire! Fire!|
At this point, let's take a breather and consider what we really wish to accomplish. From this article's perspective, we're looking for a spell to permanently end the zombie threat - in other words, to "kill" the zombie. We know from other sources that in order to do this, one must destroy the zombie's brain, therefore we will concentrate on that goal. While kinetic energy spells (such as levitation and/or push-back effects) may have their place in combat with the undead, simply throwing zombies around will not usually permanently destroy them unless you're fortunate enough to be able to levitate a zombie into boiling lava or something.
|Reducto - to dust!|
While examining the usefulness of each effect, one must also consider the tactical situation at hand and consider any unintended consequences. For example, in a close-combat situation with multiple attackers, you probably don't want a cloud of burning hot ash obstructing your view, or landing on your skin. In this case, you may be better off with going with a vertical wand flourish and slicing the zombie straight down the middle. As long as the cut goes through the head, it will slice through the brain and destroy it, granting you victory. For multiple zombies, you might be able to accomplish multiple kills in one cast by using a horizontal flourish at about eye level. I wouldn't want to be the person to have to clean up that mess, though.
As for the shrinking effect, further research and caution is definitely required. We simply don't know yet if the zombie brain can still function after being reduced in size this way. If you're going to try it, be sure to shrink them to a size where they can be easily squashed under-foot, and be sure you're wearing strong shoes that can't be bitten through. The virus that causes zombification in the first place can almost certainly be passed through a puncture wound or bite to the foot, regardless of the size of the biter.
For longer range open-air combat, the obvious choice is the incineration-to-ash effect. The will probably work best if you're upwind of the zombie horde and atop a structure they won't be able to climb. You can simply perch up there and take them out one-by-one until all that remains is a giant pile of smoldering ash. Your only limitation is the range and accuracy of your wand, which we will now discuss.
Your typical wizard's wand is, at the very basic level, a handheld piece of wood infused with some sort of empowering magical core. All of the spells we've discussed need to be aimed by the wizard - there are no "fire and forget" charms or "smart spells" known to the wizarding world. It is also well documented that spells and especially curses can not only miss their intended targets, but also reflect off of certain surfaces and sometimes fly off in unexpected directions similar to a ricochet or stray bullet. Therefore, in any magical combat situation, it is important to have a precise and accurate aim, as well as finely-tuned situational awareness.
Since your typical wand is held in a single hand, it can be assumed to have roughly the accuracy and accurate range of a typical handgun - about 6 or 7 meters. Of course, when the I first made this connection, a Jacob's Ladder of brilliant ideas began to buzz inside my backwoods, redneck-turned-engineer, firearm-loving brain.
At first I thought, why not fit a wizard's wand with some optics - a scope, for example. But why stop there? Why not add a laser site?
Then, it hit me. What a wizard really needs for effective zombie combat is a long-range wand with an advanced tactical sighting system that can be extended and adapted to meet his or her individual needs as situations arise. What you need, young sorcerer, is an assault wand!
Alternatively, it may be possible to simply attach a wizard's existing wand as an accessory to a traditional tactical rifle. The best place for this would probably be on the forearm of the rifle since the wizard would then be able to maintain the physical contact with the wand itself that seems to be required for spell casting. Conveniently, this position also offers close proximity to the barrel and, therefore allows spells to be aimed just as precisely as bullets without having to adjust the rifle's sights.