If you're looking for something unique and quirky, check out the Museum of Unnatural History in the 826DC space. Their selection changes regularly, from shirts to books to posters to other interesting and useful (or completely useless) stuff. I wrote about them when they opened too.
For the active person, check out Nash's Sports on 14th north of Park (in the Tivoli building). They have jerseys, athletic shoes, sports clothes, balls, and other similar stuff.
If you are looking for somebody who enjoys their beer and wine, try D'Vines at 3103 14th Street NW, which sells lots of wine plus craft beer.
There's a few spots for clothes too: on the southern end of the hood is Palace 5ive at 2220 14th, the skateboard shop which also has hip shirts, pants, hats and shoes. Martha's Table at 2214 14th has a thrift store too for vintage clothes.
Gift cards are plentiful in the hood too: most restaurants offer them, plus there's coffee cards at Starbucks.
And it goes without saying that there's Target, Best Buy, and
Any other recommendations?