Making a gift is very personal and often appreciated more than something bought. If you have kids, a homemade present from them will be loved forever. Have a look at www.mykidcraft.com for some inspiration.
I like Oxfam goats and "experience" gifts (eg. dance lessons, a trip somewhere) which don't take up space and create memories. My parents very generously gave us our car registration for Christmas, which was different and very much appreciated.
Personalised cheques where you give up your time as part of the gift is a unique gift idea. Hand make and write cheques out to suit the family member you are giving it to. For your mother, it could be taking them out shopping for a day. For a father it could be a day out on the golf course or a fishing trip. Gifts can range to having a coffee to watching a movie to a few hours babysitting. Use your imagination and cater it to the recipient.
I definitely agree with Claire and Pauline that handmade gifts are the ones that are most meaningful, both for the giver and receiver. These days, with such a huge assortment of items available from around the world, I think that the personal aspect of giving gifts has been largely lost. Making your own gifts doesn't have to be difficult...there are so many books and websites available full of fabulous and easy projects. If I really haven't got the time to make a present, I'll try to buy someone else's beautiful handiwork from a local market or get something from somewhere like Oxfam, where the money goes to helping people in developing countries.
Some unique gifts can be things that they always aspired for but never thought of buying. For examples, my sister always wanted a sewing machine but never bought one so for Christmas I gave her a sewing machine. Unique gifts are gifts that speak volumes about the heart and do not have to be very expensive.
anything Handmade e.g. cards, quilt, etc....or homemade goodies e.g. cookies, jam, tarts. I think it's more meaningful to give something from your heart - something you put in an effort to make, it doesn't matter big or small.