Source made it so it doesn't penetrate through any surface unless it's 1 pixel thick, or made with the "glass" material.

Only the sniper guns can hurt players consecutively, and at close range.

Basically depending on the gun it will penetrate a certain number of in game units. The awp can shoot through 20 of such, the CT's starting pistol goes through 2 of such. I can't remember any of the other values.

Incorrect. You can gain a multikill with any weapon other than the knife. You can get a double glock kill. You can get a double flash/smoke kill.

Weapon	glass/prodwndwa	tools/toolsblockbullets tools/toolsnodraw
M3	1	1
XM1014	1	1
USP	15	6
Mac-10	15	6
UMP	15	6
TMP	20	8
Glock	21	9
Elites	21	9
MP5	21	9
P228	25	10
Five-Seven	30	12
P90	30	12
Deagle	30	12
Galil	35	14
Famas	35	14
M4-A1	35	14
SG 552	35	14
SG 550	35	14
M249	35	14
AK-47	39	16
Scout	39	16
Aug	39	16
G3SG1	39	16
AWP	45	18

You can also shoot through wood and other materials. Concrete acts like the second column.

Haha yea I've made walls 8 thick and you could still shoot through them and I've gotten 3 people with one round with the awp

and i didn't know you could kill with flash's and smokes :S i knew you can hit people with them but i didn't think it did any damage

Yes.