I started on the light version of Pspice which I actually thought was good, though most people I talk to do not like it.
I then moved on to the advanced Cadance spice simulator for IC design which is the best one I have used to date but I am not about to shell out for that seat.
Then I moved on to the Altium design suite built in simulator, which I must say is hands down the worst spice tool I have ever used.
I now have now settled on using Multisim. It is not perfect but there are some very nice interactive features that I enjoy.
One that I have not tried which many of my co-workers like is LTspice by linear technology. I think it is free as well.
For RF simulation I would recommend Microwave office but again you are talking serious cash(and they don't even give you a permanent licence, you actually have to go back to them every year to get your renewal licence).
Hope that helps