I use "gift mate" bags. These are lovely strong plastic bags, some are decorated with a Christmas theme, others are more general, some say "party" or "celebrate". They range from small to large in size, [from about A6 to A2 in paper sizes] and can be tied shut at the top with their inbuilt ribbons.
I saw them first on Ideal World shopping channel, and then found them on Amazon.
I also use Christmas carrier bags from Supermarkets. Very cheap!
And I buy decorative stronger plastic shopping bags from, for example, Poundland. For, erm, £1...
If you have a very large present, the LIDL supermarket bag is the biggest I have seen.
These can be tied shut with ribbon [or even stapled, if you run out of ribbon!] at the handles. With a bow and a gift tag as decoration they are easy to use, fit almost any size and shape of gift, and act as part of the present - because they can be used later.