I have heard different things from different sources on what Agility affects. It definitely affects Guns skill, Sneak skill, and AP. However, some sources claim it affects walk/run speed in the game. Trying to test this, I haven't really noticed a difference between 1 and 10 AGI. Does anyone know for sure?

According to the manual it is small guns,sneak,and AP for Vats.

That's not something I've ever come across. I'd say your sources are wrong. If you can't notice a difference between 1 and 10 then it seems pretty obvious it has no effect.

Agility:

AP regenerates faster, you holster and take out your guns faster. It affects Guns/Sneak skills, it affects how fast/slow you run.

There's probably some other factors that I'm missing. Nevertheless, it's a great skill to have.

Not according to the Portal at least:



I'm don't know where you get this info, but I'm pretty sure it's wrong.

I could be wrong but from what I have noticed; and in my humble opinion, OPPONENTS or targets move slower or faster in response to your targeting them with a weapon.
It seems to me at least that the higher my agility is; the slower an opponent will move in response to me trying to shoot them. Sometimes I am forced into using the VATS
system because a target is dancing like mad and I can't get a good shot off ! High agility for me slows them down it seems. Thats why I try to make my agility high.