Emory Peak in Big Bend National Park is the the highest peak in the Chisos Mountains, reached by a long day-walk. It can be combined with the South Rim, Southeast Rim and Northeast Rim for even more spectacular views.
The Chimneys trail is fairly uninspiring, with the payoff being some nice views and hidden Indian petroglyphys once you reach the long rock outcrop.,
Lost Mine Trail is a steep walk up to a ridge, rewarded by stunning views over the Chisos Mountains and out toward Mexico. Go early or late to avoid the crowds.