My five favorite SI tools, the ones I use the most are:

1.      Keysight ADS

2.      Mentor HyperLynx

3.      Simberian Simbeor

4.      QUCS

5.      Teledyne LeCroy SI Studio

 

If I could have 4 more in my list, they would be:

6.      Ansys HFSS

7.      Mathworks MATLAB

8.      Polar SI 9000

9.      Keysight PLTS