Sem86 is an innovative x86 full-system emulator that allows dynamic loading of instruction behavior for better emulation of undefined and undocumented instructions. It is significantly faster than Bochs and offers a unique capability to bisect execution to analyze differing instruction behaviors, making it valuable for applications like malware analysis. The emulator runs various operating systems, including Windows and Debian, and is compatible with Android devices, though it may encounter memory issues on lower-end phones.