Favorite strings?

These Kirk Hunter Virtuoso Ensembles are my new favourite > https://www.kirkhunterstudios.com/products/virtuoso-ensemble/ 
 
They are also on 70% off sale until tomorrow ($89 instead of $299) and take up less than 3Gb of disk space.
 
I have been using Miroslav Philharmonic CE ( http://www.ikmultimedia.com/products/philharmonik2ce/ ) and EastWest Hollywood Orchestra Silver ( http://www.soundsonline.com/hollywood-orchestra ) before this, both of which I like but Miroslav is easier to work with for a quick ensemble part IMHO. These are the entry level products which still sound good enough to my ears as I am not using them to make a living.
 
You can spend more (lots more in some cases) to get better quality e.g. Gold/Diamond versions of EastWest products and full Miroslav but the entry levels might suit and also check the disk space required by the pro level libraries.
 
Others can probably advise on the more Pro level libraries.
 

If you're asking for "favorite" as opposed to least cost...
 
This one goes in the favorite category: https://sonuscore.com/shop/the-orchestra/
 
Here's a YouTube clip to see: https://www.youtube.com/watch?v=3x1DKsMyJkM
 
Not the least cost, but great, worth it if you can swing it.

Not the popular choice and can be a pain but 8Dio Adagio, Agitato and Anthology. Love the sound.
Embertone Quartet, plus I imagine Joshua Bell which I don't own cause Fleer knows what he is talking about.
I will respectfully disagree on The Orchestra as to me based on demos it is clever but lacking in tonal quality. Inspire sounds like the 1927 Yankees played.

I really like the free Virtual Playing Orchestra.  It is a big step up from Rapture! 
 
http://virtualplaying.com/virtual-playing-orchestra/
 
Section and solo instruments.  Sustain, normal, staccato, accented articulations for all strings, brass, woodwinds.
 

Virtual Playing Orchestra is a free orchestra sample library, in sfz format, that attempts to emulate multiple articulations of the solo and section instruments from a full orchestra using the best free samples from Sonatina Symphonic Orchestra, No Budget Orchestra, VSCO2 Community Edition, University of Iowa, Philharmonia Orchestra and extra free samples from Mattias Westlund, author of Sonatina Symphonic Orchestra.

 
 
 
 

G

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

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

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>!

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

Dang, been looking for those all my life.

Haven't dared to try yet, but Rev Robin Trower shared his secret, and made sense as to why I couldn't tune to some E flat or something key to play along with his incredible songs.
 
Uses 10 gage strings but detuned to D. Hi action. That's how he did it and still does it. Highest respect to this incredible musician. Don't know if he thinks he is still channeling the ghost of Hendrix, but if you can play like he does, channeling anyone needed is a valid resource to rock on.
 
John