what is the betagun

[Lanson]

?

[Balim]

It is the Bug Bait in an error state. It is a problem in Synergy dedicated server which occurs when the server changes from Half-Life 2 to HL2 Episode 2 and back to Half-Life 2.
This can be fixed server-side if the host puts on some of the fixes that have been developed over the years.