I can come up with 1001 things to do with a bottle of Grand Marnier or Cointreau, MS, and as all of them are very more-ish you might want to invest in another bottle or 6.
Pour 20ml any orange liqueur, 10ml fresh lime juice, 20ml cranberry juice, 40ml vodka into a cocktail shaker, fill with ice, shake vigorously, strain into a martini glass, and garnish with a twist of fresh orange for a perfect Cosmpolitan.
30ml any orange liqueur, 30m lemon juice, 30ml brandy or cognac shaken with ice and strained and garnished as above will give you another classic cocktail that was once immensely popular, namely a Sidecar.
Or try one of my favourites - strawberry and mint fizz using
50ml any orange liqueur, 15ml fresh lime juice, 6 strawberries and 3-4 mint leaves.
To borrow a word from sw, 'muddle' the strawberries and mint leaves in the bottom of a shaker - this is easily done with a pestle (or similar blunt instrument). Add the lime juice, fill with ice, shake vigorously, strain into a highball glass and top with soda water or any good brand of carbonated mineral water such as Perrier, San Pellegrini or my aqua of choice which is Badoit.
Try to save some of your precious orange nectar for classic crepes suzette, or orange glazed fresh strawberry pie, chocolate fudge tart with orange sauce, blueberry coffee cake with orange glaze, chocolate orange cheesecake, cranberry-orange bread with orange glaze... the list of goodies is endless.
If you incline more to savouries, consider orange glazed pork tenderloin or duck/chicken breasts, cola baked ham with mustard and orange glaze, glazed salmon, orange glazed sweet potatoes or carrots.. again, there is an extensive selection of delicious dishes to tempt you and I can supply recipes for any of the above.
Btw, if you have fresh strawberries of the somewhat indifferent variety, hull them, put them in a bowl, sprinkle with sugar and pour some fresh orange juice over them, place in fridge for 3 hours or so gently turning the fruit every hour and you'll find the flavour is immensely improved - and more especially if you pour a little orange liqueur over them when serving or add it to an accompanying jug of cream.
If you want to try a Dorian Grey the cocktail guru suggests 20ml orange liqueur, 20ml white rum (Bacardi or similar), plus 30 ml each of cranberry and orange juice poured over ice in a highball glass and stirred a couple of times.
There is another version of Dorian Grey which is simply equal parts of sweet vermouth, green chartreuse and gin with a splash of blood orange bitters but I reckon that one may be best drunk in front of a mirror the attic where the portrait is kept 
Pa comes into his own during high days and holidays but I refuse to think about the festive season until after Labor Day. However, you may rest asssured, there will be treats to suit every palette and cater for every climate 
Tomorrow I shall reveal a special concoction for the dc and lns and, of course, dps and other relatives can clandestinely add a little something of their choice to their glass 