Some are really bizzare while a few seem understandable. To make it easy we could address them as if they are in a grid, A1, D3, B4 etc.
Some obvious ones are (A3=Drinking a soda from a vending machine), (B3=Disturbing the guy in the bathroom) and (C2=Perhaps killing five enemies with one grenade?). D3 probably has to do with the Tau Cannon or Gluon Gun.
I bet the 3 that are black, on the right corner are Xen achievments 
Are you joking? Maybe they are black because they are not actually there.
Mabilis fails at understanding jokes.
Don’t worry, keep at it and one day you’ll catch on.
Well, shit.
ahahahaha
Well, you were on the right track with ‘Are you joking?’ And it could have been worse - at least you aren’t one of those people that cites The Onion to support a public policy position.
Oh goodie. Shall we begin wild speculation?
That turret with stars and moons could be “Do not trip any turret tripwires in the course of the game”.
Mediazz !
B4 = Find Gordon’s helmet?
B5 - Kill 50 Rats with a crowbar?
B6 = Overcook the cassarole (He does look like he has a chef hat on)
D5 = Keep a rocket in the air for a certain length of time…
E5 = Either kill no headcrabs during the game or tame/debeak one and let it follow you to the end of the game.
Haha A1 is awesome I bet when the game comes out only we people who know this forum all too well will understand the achievement.
A1: ‘Late for Work’
-Start up Black Mesa
B6: Applied Physics
Kill an enemy with a physics object.
I’d say for B3…
One Man Bomb Squad - Kill 5 Enemies with a single grenade.
I have to say, I’m pretty stumped by the purple top hat at A2.
You have to find the purple top hat in the game and then it unlocks in TF2.
willy wonka’s hat?
…maybe candy/choccolate vending machine lol
It makes me wonder if these are joke or rejected achievement icons. After all, they’ve been as tight lipped about them as they are about Xen, so it’s kinda strange they would just publicly upload them like that.
A2 - rutta hat? (there is a “Rutta Grape” soda machine) It’s apparently an inside joke.
https://www.blackmesasource.com/404/hatkg3.jpg
https://www.blackmesasource.com/404/ruttaruttahat.jpg
https://www.blackmesasource.com/404/jimmygfys7.jpg
https://www.blackmesasource.com/404/ruttack0.jpg
https://www.blackmesasource.com/404/purplehatyi0.jpg
I thought it had to do with baiting an Ichy.
It’s Gordon’s pimp hat.
/toolazytoshop
They’re waiting for you, Gordon, in the the pimp chamber.
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.
