Air on

Get you some free Xpand!2 here until Nov 30th.  There are quite a few string patches among the supplied 2500+ presets. 
 
https://www.kvraudio.com/...il-november-30th-38798

I thought you were talking about guitar strings!!
 
GHS Nickle Rockers 11's

Yet I preferred Bach’s (and Wilhelmj's) Air on G String ;).

Fleer
Yet I preferred Bach’s (and Wilhelmj's) Air on G String ;).

Going where no man has gone....

Of course, you could try the strings in the FREE Sketching Orchestra from 
Large Feline...

http://bigcatinstruments....chamber-orchestra.html

Favorite? That depends entirely on the context.
 
I have some go-to heavyweight orchestral libraries for serious orchestral arrangements, but they're not worth the bother when all I want is a pad behind a pop vocal. At the other end of the spectrum, I also like Indiginus' Solid State Symphony, which sounds synthetic but is a very quick and easy addition to a project. In between are string patches in Omnisphere, which sound authentic but aren't very programmable.

As Bit points out, this is a very context specific question! If I had the money I'd probably own half a dozen libraries to cover all the bases, but alas I don't.

I use the 8Dio Adagio/Adagietto/Agitato series a lot, especially for smaller string sections. I absolutely love their dynamic bowing patches, although they can be very frustrating to use. I did take advantage of the cross-grade to Anthology, but I'm so accustomed to the previous versions that I haven't really given it a fair shake.
 
For larger sections I use Cinematic Scoring Strings, and they just work. They don't have quite as many articulations, but sometimes that's a good thing. And they sound absolutely gorgeous, and they are really easy to learn. There is just nothing negative to say about this library.

Recently I picked up Alex's Cinematic Studio Strings and they do give 8Dio a run for their money. They are far easier to use, but sometimes I really do want the microscopic control I get with 8Dio.

For rock and pop productions I still use Kirk Hunter's Rock and Pop Strings, or Native Instruments Session Strings. I have the basic version, and quoting Bit again, for simple pop arrangements both work quite well, you can get a little more detail with the KH library, and it is appropriately aggressive.

I started with KH Diamond, later upgrading to his Concert Strings 2. I no longer use them, although they are still on the hard disk because every once in a while I think they might be just the thing. I think my tastes have changed, because I always seem to gravitate towards my other libraries for strings, brass, and winds.

Depending on what you are after I should also mention the ensemble type libraries - I  have Albion One and Orchestral Essentials 1 & 2. I struggle a little bit with using them because my brain just doesn't work that quickly, and i need to think in terms of sections - a shortcoming on my part I'm pretty sure. They do sound gorgeous though.

Needless to say, I've left out LASS, East West, Orchestral Tools, Cinesamples, and others which I don't own. They all have their good points.

Some might say it is a problem to have so many choices, I'm not sure it isn't a good thing<G>!

Very subjective matter but since you asked, my favorite is NI Session Strings Pro but only for pop and R&B work. I wouldn't use it for orchestral work.

When I seen this I was going to answer Ermie Ball regular slinkies.