Quoted By:
other central texas things that have not been mentioned that are nice are pedernales and colorado bend state parks. the ladybird johnson wildflower center is great if you like flowers.
people have mentioned palo duro, but there is also caprock canyon which is similar but less visited. they also have a 54 mile trailway which has some really nice sections.
for primitive camping or backcountry use, its either flat national forests in east texas, leaving the state for like arkansas, or going to west texas, where i live. guadalupe and big bend (both state and national parks) are great, and there are a bunch of wildlife management areas in the west that are pretty unused outside peak hunting times. you can get your shootin on there. i go to black gap a lot when its not too fucking hot.