Private unique tour recommendations for Barcelona?

There are plenty of options... I can speak of http://www.runnerbeantours.com, they offer both of-the-mill tours and private tours. Quite a few acquaintances that have visited and used them have been very happy.

Julie, just how private and how unique do you mean? You might look at www.taste-barcelona.com. Their tour is ecstatically reviewed on TA and is at least small and unusual, if not actually private and unique. I will be with them on April 12 myself.

Hidden City Tours - best tour we went on in Barcelona.

Just for clarity, as the word "official" used above might cause misunderstanding: 'official' tour guides are individuals that have passed an exam run by the government that accredits them as knowledgeable to perform such duties and that, as stated above, they're registered and during a tour can accompany clients into public museums while acting as guides. Period. This of course doesn't certify one's abilities to communicate, or one's quality providing this service.

Non-official guides cannot enter into public museums/attractions while "doing a tour" with clients (note the word "public" which doesn't include private premises -unless they've got an agreement with the City Hall not to allow non-official guides), and also since nobody accredits their knowledge, can indeed be cowboys that know little about the city and provide a lousy service... or can be enthusiastic and passionate people that love to share their knowledge and legally earn a living on it but didn't bother to jump thru the loops of going thru the formal procedures... which btw, isn't illegal! On top of that, if (if!) they are good communicators, the result to visitors that hire them can be an excellent experience.

Disclosure: I have no relationship whatsoever to neither my earlier recommendation nor any other similar service. I'm just fond of a free market economy ;)

I take the opportunity to mention another of those misuses of the word "official"... hop on hop off buses. In Barcelona there are two companies offering those services: Bus Turistic -which happens to be owned and run by the local government- and Barcelona City Tour -which is owned by one of the top private tourist services providers in Europe. The first one constantly shoves down everybody's throat that they're the "official city tour"... however, both offer pretty much the same service, run approximately the same routes, have similar prices, use the same type of double-decker buses (different colour though!), and both are terribly (really, terribly!) demanded during summer months... so I am not too sure I'd use them in July and August if you don't like this at most stops.

Having the grit to take the courses and exams for official certification counts for me. It not only shows they are serious but also professional. If there is another way to validate the professionalism and knowlege of the others beyond word of mouth and TA please let us know. Studies have shown that fifty percent of Trip Advisor reviews are tainted, so you can't count on that. Thanks for the clarifications wonderful and Enric.The others may be the nicest people in the world and tell good stories, but I prefer someone who's certified.

Finally, too many of the "free" walking tours are lead by young people who are given scripts and told they can keep the tips. How exactly is this Runner Bean run? Does anyone have details?

Check out Eatwith.com - meals hosted by a local in their home

That's fair Bets... but I'm not advocating for or against accredited tour guides nor independent tour guides... since, in the business of telling stories to entice an audience (which is what this is all about) at the end of the day the person actually guiding you is who'll make it a memorable experience or not -not his/her titles or accreditations.

I only think it's worth mentioning to would-be users that the use of the word "official" instead of "accredited" to refer to accredited guides can be (is!) misleading because it might imply that those not accredited -hence "not official", which might be perceived as derogatory- would automatically be something illegal, bad or unreputable and to be avoided and that is not necessarily so. Sadly, we have several other experiences in this sort of ill-intended "classification" by which these -the official ones- are good and the others are bad, namely taxis and Uber, the above-mentioned example re:hoho buses, or hotels and the Airbnb-like listed direct owner-to-client apartments, etc.

About 10 years ago on my first trip to Barcelona I took a Gothic Quarter tour operated by the city TI. It was a good tour. A couple of years ago I was in Barcelona with a friend who wanted a tour so we took the Gothic Quarter tour offered by Runner Bean. This also was a very good tour. However, I felt the Runner Bean guide was much more enthusiastic and every bit as knowledgeable as the city's "official" tour guide. I would never hesitate to go on a tour with Runner Bean.