Audio Assault is giving away Grind Machine II for nothing, but hurry as it looks as though the offer is only available for a short time.
The amp sim is designed for the heavier end of the electric guitar-playing spectrum and features a wide variety of high-gain models that are not too dissimilar to some well-known classic amplifiers.
A total of 15 preamp simulations are joined by 15 cabinet impulse responses and, of course, you can add your own cab models to the IR loader.
The desktop app is free (standard price $49) and available for Windows and Mac systems in VST/VST3/AU/AAX formats. Head over to the Audio Assault website to download yours.