Who are the seconds of famous players? Can anyone provide lists of seconds of famous players? They can contain the names of people that work/worked with top players for a long period or for a particular match/tournament. Besides the names of the seconds, I'm also curious about the typical strength of seconds and whether there are seconds that worked for different top players.
Thanks in advance!
Just to get started, of the top of my head:


Magnus Calsen worked with Jon Ludvig Hammer,  Laurent Fressinet, Ian Nepomniachi, Peter Heine Nielsen, Michael Adams, Simen Agdestein, Garri Kasparov. He also had training sessions with Ding Liren and Wesley So. Also, this were his seconds for WCC 2016.
Vishy Anand worked with Peter Heine Nielsen, Rustam Kasimdzhanov,Radoslaw  Wojtaszek, Grzegorz Gazewski, Krishnan Sasikiran, Peter Leko, Surya Ganguly and Sandipan Chanda. He also had at least one training session with Magnus Carlsen.
Kramnik worked with Peter Svidler, Miguel Illescas, Evgeny Bareev, Peter Leko, Sergey Rublevsky, Alexander Motylev, Efimenko.
Veselin Topalov worked with Cheparinov, Paco Vallejo, Dominguez Perez, Romain Edouard.


As you can see the rating of these seconds is generally in the 2650-2750 range. (A notable exception would be Kris Littlejohn, a 2100 player who used to assist Hikaru Nakamura). It is quite common for seconds to work for different top players, at different points in time. (Leko, Motylev, Nielsen, Kasimdzanov … from the list above.)
As for the strength of a second, they are typically very strong theoreticians. And often a new second is hired because he is a specialist in a particular opening.This is the main reason why his name might be kept a secret. For example Dominguez is an expert in the Grunfeld and the Najdorf. Michael Adams was clearly hired because of his expertise in the Berlin Defence. Gajewsky introduced a strong counter gambit in a line of the Ruy Lopez …