Haven't lived there in 5 years, but here's my suggestions:

- Get BBQ - agree that Gatlins or Killens are good.
- Go To Pappasito's for Fajitas - Yes it's a chain, but their fajitas really are amazing. Do not get anything else. Only fajitas, preferably with a variety of meats.
- Galveston - Not the greatest place and beaches are sub-par if you're from California or Florida, but if you've never been to the gulf it's worth checking it out just to say you've been. There are some decent seafood places there. If you're willing to pay for it you could go deep sea fishing too.
- NASA - Won't blow you away, but if you've never been to NASA it's worth seeing.
- Museums - Houston actually has some great museums. The Science center and Art museum are particularly good.
- Brazos bend - not beautiful and it will be uncomfortably hot. But if you want to get some pics close up to gators you could swing by here. It's kind of out of the way though. Often gators are just sitting there on the walking paths, but it can be hit or miss. You're taking a gamble by going there. Depending on the number of gators out it can be neat. But you risk walking in the heat to see only a couple in the water. You never know how active they'll be.
- Houston's famous deli - hole in the wall place near the stadium, but has a fantastic Muffaletta sandwich. Don't get anything else.
- If you want to take a roadtrip you could drive to San Antonio to check out the Alamo and riverwalk. Stop at Bucky's on the way to get gas and pee in luxury.
- Chicken wings and waffles - if you want to experience some southern cooking, get wings and waffles at the breakfast club.