Many homeowners are tempted to wrap their air conditioner condensers (the outside unit) to protect them over the winter. But wrapping an A/C condenser is never a good idea. Steel rusts, and wet steel rusts even more. Even when wrapped tightly, your condenser isn't airtight. So moisture gets trapped under your tarp and condenses on the inside of the unit. The moisture on your neighbor's condenser is free to evaporate.
Covering an A/C condenser also encourages rodents to move the family into new digs where they're protected from the elements. Once they're settled in, they'll gnaw on the compressor wiring and insulation. Come spring, you'll have a stinky cleanup, a rusty A/C condenser and a hefty bill for rewiring.
If you want to protect the unit from falling icicles, just place a piece of plywood over the fan guard and weight it down with bricks. If you want to protect the metal and keep it looking good, give your condenser a coat of car wax before the snow flies.