[quote=Yog Sothoth]
can someone please explain why so many anime characters shout out their attacks? it makes no sense, by doing that they give away what their plan of attack is and gives their opponent an idea of what's to come. strategically it is very not smart.
[/quote]

Depends on the anime you are talking about. In most cases, it is a manga tradition so readers can understand what attack they are using. It is also something similar to when chess player call out their moves. You mostly see this in ki/energy based combat and card games. In a manga like...Claymore, I don't think they call out their attacks.

In an anime context, certain moves are used as indicators so the shout out is for dramatic effect. Also...try to find a 20 year old person that has never heard of a Kamehameha wave. Hell, they may even act it out XD