Strange Weapons?!?

[Fragimus_Max]

I just got a Strange Stickybomb Launcher.

I have noticed that a few players have weapons that go up in "Kill Levels" and keep count of their kills. I believe this is one of those types of weapons.

I wonder: 1) how rare they are, and 2) what effect, if any, do kills have on each weapon? Do some of us FINALLY get special effect items? I sure hope so!

http://www.tf2items.com/id/fragimus_max

 

[Micnax]

1. You get them from crates randomly, in Series 19 and up.
2. The kill count just goes up in progression, see the ranks here.

 

[Fragimus_Max]

1. You get them from crates randomly, in Series 19 and up.
2. The kill count just goes up in progression, see the ranks here.

So how rare are these compared to, let's say, landing an unusual hat? Or is every uncrated weapon from this point on going to be a "strange"?