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Get a knife you'd actually carry. A lot of the alternatives are great if you're wearing jeans, a jacket, or other "heavy" clothing. But as you live in Brazil, I take it that you'll wear a t-shirt and shorts a lot. Thus, I'd recommend a Benchmade 530 or 531 as they're light and thin folding knives with a great blade. Just make sure you get used to their small thumb studs. I love mine, at least.
And, of course, be realistic. I don't know how much you make, but all American, German, or Japanese (even Chinese) knives will be expensive. Whatever you can get your hands on with a blade that lasts, that you will carry, is the best knife. Even if that means a weird knock off from Gabriel deep in the Favela.
