A remake of Gear's aurora_city, at a first glance it might look innocent but it has quite a few teleports and secret camping areas that will keep you moving and ducking for cover.
It contains the UMF building that was featured at the E3 presentation prior to HL2 release, in which the player yanks the letters F and U with a WIP ggun and throws them at a strider, to the audience's delight.