Everybody seems to be interested in the string combos of artists (including me of course!), so I did some research to try and find out what they used including newer and older artists. Enjoy and if anyone knows of anything different than what I have posted, please let me know.

Jascha Heifetz : Goldbrokat Medium E, Plain Gut A&D, Wound G (don’t know the brand). That he used until the end of his performing career judging by the album photos from the 1960’s that I saw.

Nathan Milstein : Same as Heifetz in the 1950’s with a Eudoxa G, but he moved to using an Eudoxa G&D, plain gut A and Goldbrokat E in the 1960’s. I have been told by someone who saw him in the 1970’s that by then he was using an Eudoxa A as well.

Zino Francescatti : From an album from the late 50’s or early 60’s that I saw, he was using a Eudoxa G, Kaplan Silver D, Eudoxa A and Goldbrokat Medium E.
David Oistrakh : Eudoxa D and G, Prim Steel A (or Chromecore) and a Prim E.
* On a historical note here, the first person to use and recommend the use of a steel A with two wound gut core lower strings was Carl Flesch.

Arthur Grumiaux : Used an Eudoxa A, D, G. Couldn’t figure out the E. In the 1970’s, I saw a cover where he used the Eudoxa steel A, and gut on the two lower strings.
Henryk Szeryng : Used a Eudoxa D and G, a Kaplan A and either a Gold Label E or Kaplan E (they look so alike!). He did also use Olives for the D and G, and on the last filmed broadcast he did for Radio-Canada, he used Olive D and G, plain gut A and a Gold Label E from what I could tell.

Isaac Stern : Used the Eudoxa A, D, G and a Goldbrokat Medium E. Later in his career he kept the E but switched to Dominants.

Frank Peter Zimmerman : Uses Olives for the A, D, G and a Hill E.

Thomas Zehetmair : Unless he has changed, he use to use a full set of Olives.

Pinchas Zukerman : Used Eudoxas until the Dominants came out which he still uses (including the E, I think...). He was the first soloist to switch to Dominants.
Itzhak Perlman : Used Eudoxa in his early career than switched to the traditional combo of Dominants with the Gold Label E.

Hilary Hahn : Dominants with a Gold Label E.

Maxim Vengerov : Used to use Dominants but recently switched to a full set of Pirazzi.

Vadim Repin : Don’t know what he used before but he is currently playing on a full set of Pirazzi.

Ilya Gringolts : He uses Evah Pirazzi at the moment.

Gil Shaham : Uses Dominants and a Jargar E (don’t know which gauge).

Midori : Uses Dominants and had a Synoxa E for a while, but it could also be Jargar Forte E which looks similar.

Stefan Jackiw : Uses Dominants and a Jargar Forte E.

Ricci: Now using Vision strings (thanks for Buri for letting me know - he saw it in Strad magazine). In the past he has played Dominants, and before that, Eudoxa.
Anne-Sophie Mutter: Dominants with some kind of E... looks like a Gold Label or Golden Spiral.

Joshua Bell: Now listed by Pirastro as a Pirazzi user.

Julian Rachlin: Said on this site that he uses Tonica D&G with a Jargar A and a Kaplan Golden Spiral E.

Cho-Liang Lin: Started his career on Eudoxa, but quickly switched to Dominants (including the E as I saw on an old CBS LP cover), and is now using Infelds which he finds more reliable (according to his statements in Strings magazine).

Aaron Rosand: Listed on the Pirastro site as now using Tonica Weich (Silver D) since the late 90's. Strange though as he swore by the traditional Eudoxa G&D and the pure gut A with some E until then. Even forced his own students to use that string setup.