Dass130,095 Locked 21 Oct 2016 26 Nov 2017
This achievement is, as of 2016, unobtainable. The original way of achieving it was by grabbing gifts dropped by opponents (bots or other players) after you killed them. The achievement was tied to the Winter Event of Christmas 2011.
Since then there have been many discussions in possible strategies of how to get it, with one consisting of changing the PC date to Christmas 2011, but it has since been proved that this won't work. Just check the old Steam forums or the Steam Community CS:S discussions and you can see the frustration around this single broken achievement.
People who are getting this achievement in recent times most probably cheated using an unlocker.
Edit: As of 2017, there is a new way to get this achievement without using an unlocker, you can change the version of the game. Some achievement stats sites are not allowing this method, and I'm not sure if TSA allows it as well, so you need to do it at your own risk.