RealGuitar (MusicLab) is the most critical non-Sonar VI I have. It will play any strummed acoustic guitar part you can imagine (unless it would no be playable on an actual guitar). It also does good solo and finger picking parts, but I have several keyboards and sample libraries that will do that. Strumming is the hard part and RG makes that easy (once you get the concept).
Vir 2 Acou6tics sounds great, but I find it and Electri6ity a little harder to use.