Doomsday Engine

Pretty much what the subject says; in the latest unstable build (1119) when anything moves in a multiplayer game, monster or player (though the player can mouselook around without issue), the client segfaults. Though the server remains running.

Also if one fires a weapon right before it segfaults (i.e which alerts monsters who promptly move and cause a crash), the player is unable to re-join until the server changes maps; otherwise it seems Dday tries to immediately repeat the gunshot, which caused the crash the first time, with the same fatal results.