I tried the various "free" ones that came with SONAR over the years (Guitar Rig, ReValver) and never got anything I liked, so I stuck with my aging POD Pro. Then I found the Blue Cat Free Amp and got some sounds I liked a bit, but not too much, and Nomad Factory Rock Amp Legeds, but I still wasn't really happy, so wasn't actually playing much guitar.
Then I tried something that @Lord Tim suggested in a thread on the forum somewhere/somewhen and started to like the "free" TH3 that came with SPlat (IIRC), so I updated to TH-U and I'm really finding I can get the kind of sounds I want now (most of the time anyway) - I do combine it with Valhalla's Shimmer Reverb for what is becoming my "go to" lead sound.