Final answer:
"Walk This Way" by Run DMC featuring Aerosmith is the song that fuses funk, post-disco, and hard rock guitar, distinguishing itself as a unique collaboration between two musical genres.
Step-by-step explanation:
The song that is a blend of funk, post-disco music, and features hard rock guitar is "Walk This Way" by Run DMC featuring Aerosmith. This track was a groundbreaking collaboration between hip-hop group Run DMC and rock band Aerosmith. Not only did the song bridge the gap between genres, but it also brought together two very different audiences, showcasing the versatility and appeal of hip-hop while staying true to its roots. The other songs listed are iconic in their own right within the hip-hop genre but do not feature the same blending of hard rock guitar.