For the record, I’m the best logo designer out there. Also never trust anyone who plugs themselves. Also never trust anyone who refers to any dot com company logo as evidence of a good designer or logo. Google and Facebook logos are practically jokes in the design industry. You really want to be talking to an art historian with a tendency towards design. Also, if you are asking for yourself, there are so many options it’s impossible to weed through them all, and it’s impossible to tell you what’s best without having a conversation with you about specifics. Also, everyone feels like they have hired the best logo designer for their company, don’t trust this, look to folks who can have a healthy balanced conversation around designers and design. If you want the best you’ll have to pay upwards of 100k to engage with folks like Landor, I’m not joking. You can also go through a service like 99designs and pay $50 and get a number of options. If you are not self aware of what a great logo is then it may not be necessary to engage in a lengthy logo and branding explore, many people do not understand the difference in end results so for them there is no reason to reach out to a big agency. Many dot com doods think a logo can be whipped up in a couple hours, some of those are even my friends. Sadly they won’t ever understand how this makes them sound. Same goes for most architects (also my friends, which is why I feel comfortable saying this) who know they can do anything but just don’t have the time. I say this not be a dick, but to tell you that a great designer will also help educate you on how you should engage in this process to achieve a successful result. I would say for the record that Pentagram, Landor, and the likes have created some of the most iconic marks. My personal favorite American logo designers would be Paul Rand or even Michael Bierut who works at Pentagram. But there are so so so many. Look for someone with great typographic skills first, then you can be sure they will create a good mark for you. A logo is so much more than a mark. And I just saw your follow up question. Right now I would say Eric Spiekermann (runs Fontshop in berlin and founder of Meta Design (largest German design agency)) is one of the best type designers ever, but check out Myfont.com for a healthy list of up and coming type designers (for the record myfont is a pretty terrible site but they have a lot of interviews). And if Hoefler & Co. didn’t tarnish their reputation by being dicks I would suggest you check them out as well. And feel free to reach out to me if you find and like my work. Good luck.