Something that's nifty is really great. You might tell your mom that the Hawaiian themed decorations for your dad's surprise party look nifty.
Nifty is informal and a little old fashioned, but it's a perfect way to compliment a cute outfit or express your excitement about your little sister's new roller skates. If a friend comments on your nifty tap dance routine, she thinks it's swell. Nifty has been around as a colloquial term for "stylish or smart" since the 1860s, possibly from theater slang.