Texas Cyclone, Batman: The Escape, XLR8, Ultra Twister, and The Viper all at Six Flags Astroworld. Batman and Ultra Twister are in particularly deteriorated condition, the rust on these two I find alarming. You can see a lot of the Shockwave blue on the otherwise dirty white of Batman.
Although the Texas Cyclone also looks particularly, grungy, it was actually painted once in the mid 1990's. What I've heard happened is that water rusted within the metal sprinkler pipes while they were painting it, and when they finished and turned the sprinklers back on, it sprayed rusty water all over the new paint. It's very expensive to paint a large wooden structure like this, so it's sat there all discolored for the last five years.