It depends on who you talk to. Sources present various products with diverse customer reviews and unequal satisfaction ratings.
BestReviews.com (which claims to have purchased every product they review with their own funds) recommends the following products:
BaBylissPRO Nano Titanium-Plated Straightening Iron
HSI Professional Ceramic Tourmaline Iron
Remington Anti-Static Ceramic
CHI PRO G2 Digital Titanium
BIO IONIC Onepass Straightening Iron
That was just one of the sites that offer reviews to hair straightening iron brands. You'll find loads of suggestions just by simply Googling "best hair straightening iron".
BestProducts.com also offer their own list. Their "experts" also mention three brands that BestReviews.com think are among the best in the market - CHI, Remington and HSI.
Tip! The key to straightening without damage is choosing the best flat iron for your hair type. Here's How to Choose the Best Hair Straightener for Your Hair, featured on Overstock.com.