If the weather is agreeable, the rooftop at Reata is hard to beat. So is downtown Fort Worth, in general. Unlike Dallas, Fort Worth's downtown area is very much alive and well.
Yeah, I know the weather pretty much rules that out this time of year, but keep it in mind for later in the year. You won't be sorry.
For those unfamiliar with Reata, it's in the building and space previously occupied by Caravan of Dreams, which was cool in its own right
http://www.reata.net/fort-worth-restaurant.html Couple comedy clubs are nearby (VERY nearby), as is Bass Hall, and at least two movie multiplexes. Makes for a heck of an evening.