[MPNumB]

cs1.6 map 1hp. Join a team, stay alive, wait for "game commencing" message, and at first round of first respawn, you can buy a weapon at few first frames of the round.

A good way to test it on listen server is to: execute "m4a1" server command at every fm_startframe, lets say first 0.2 seconds of new round after "game commencing" message. It works only first few frames of first round after first "game commencing".

Other bug, is to go fy_iceworld map, wait for buytime to pass, stand in buyzone, and execute "m4a1" at Event_NewRound. Since you didn't yet respawned, you are still in buyzone, but as far as server is concerned, it's new round, and buytime didn't pass, therefor you can buy weapons during that short period of time.