There's an exploit on zf_twilight_v2 that lets Demomen sticky jump onto an invisible roof that Zombies can't get to.
STEAM_0:0:19068837 ·٠●•۩۞۩[MBB] Mr.Hat]۩ <NZA=VRl3LlfaAI7o1^e_oLNkA>D5^H`c@?F_LkXY\j`?fVIeE4P>Q5W
exploited this for multiple games even when asked not to repeatedly. He even said he didn't care about getting banned.
Screenshots (click for full size):

Thanks for your assistance.