Valve has updated Team Fortress 2 to add cosmetic weapon effects. The Two Cities update kicks off with Manhattan which features a new map, changes to statistics reporting, more achievements, and Killstreak Kit drops that can add nifty cosmetic glows to your mayhem.
This is a companion discussion topic for the original entry at http://www.quartertothree.com/fp/2013/11/21/glowing-eyes-fiery-guns-will-power-hat-based-economy-team-fortress-2