Using a Ziplock Bag instead of a Decorator's Bag
Many cake decorating resources say you can use a ziplock bag for piping icing. I finally gave it a go yesterday.
It wasn't bad at all. I used HEB brand storage bags (1 pint capacity). It was really easy to load and held a fair amount of icing. It wasn't hard to twist or hold or to squeeze out the icing. I didn't feel bad throwing them away after just one use. The only drawback is that you'll want to cut out your corner carefully. The right angle makes it really easy to snip off too big of a whole. Use a coupler to make sure your tip is secure and all the icing goes to the it instead of spewing out the sides.
I only suggest this is you're using a small amount of icing (like for piping messages). Larger tasks (like borders) will require more space and control over the icing, which the decorator's bags are excellent for.