If you have young children, you'll want to stock up on a few age-appropriate toys when you find them for a steal. So when that next birthday party invitation comes home from school, you just pick out a toy from your stash, wrap and go. Not only do you save money, but you save the time and (inevitable) last minute scramble to pick up a gift.
If you're in your 20's or 30's, you'll want to stock up on good bridal shower or baby shower gifts. Both types of showers are easy to give gift baskets for, so when you see great deals on towels, home decorations, wine glasses, etc, pick them up and before you know it, you'll have a lovely gift basket to give. The same goes for baby shower baskets - blankets, toys, outfits, etc all can make for a nice gift basket, so pick up those items when you see them for pennies on the dollar.
And no matter your age or stage in life, it's always a good idea to have a few items such as Yankee Candles or nice hand lotions on hand to give as a last minute gift. Maybe you go to someone's house for the first time and need to bring a little house warming gift. Maybe a co-worker gave you a Christmas gift you weren't expecting and you'd like to reciprocate. These are good items to have on hand for those occassions so you aren't going out and purchasing something for full price.
If you don't already have a gift closet, keep this idea in the back of your head as you see great deals this year. You may be able to pick up a few gifts for quite a bargain!