another vote for El Yucateco, i prefer the Green, it is really nice here on the border. A bottle is about 90 cents american compared to 1.79 here in the states. And a lot better than the $3.50 i used to spend in Oklahoma. This is a really good green habanero sauce that isnt too hot. I like to pour straight from the bottle onto chips. yum.
I also like Tapatio, usually easily found in walmart around tx and ok,
Both of these have something in common, no vinegar. Thats right these are water based pepper sauces so you really get to enjoy the flavor.