It's a death tracer...it shows the trajectory of the bullet that killed you.
At the moment, it doesn't show up (and I am unable to activate it in the ma_settings menu, just lists sounds, no deathbeam)
http://www.mani-admin-plugin.com/for...ight=deathbeam explains the problem people are having with deathbeam not showing up.
gonna have to shut down the server for 2 minutes, delete a file or two and restart the server and we are all set and good to go!