Shahrukh Khan has been known to make guest appearances in films of people who hold special value for him since the start of his career. Whilst most of those appearances were just one scene roles and he wasn't required to act much, people have felt that some of those guest appearances had some feisty acting. Some of his best guest appearances (cameos and extended guest appearances included) according to us are as follows:

Shahrukh Khan Guest Appearances
Hey Ram
Shahrukh made an extended guest appearance in this controversial film at the behest of his friend Kamal Hassan, and he shined as the pathan Amjad Ali Khan. He and Kamal played archeologists in this period film. As Amjad, he left a mark on the audience and a lot of people wanted his role to be increased. That didn't happen, but 'Hey Ram' got chosen as India's official entry for the Oscars that year.
Shakti: The Power
SRK played a rustic drifter in this film called Jaisingh who helps Karisma's character to get away from all the mess that was created by her father-in-law Nana Patekar. He played the character with aplomb and stayed away from going over the top. Even though the film failed commercially, his song with Aishwariya ' 'Ishq Kamina' became a chartbuster that year.
Saathiya
Shahrukh Khan played an IAS office in the movie named Yeshwant Rao. He appears in the film very late on in the second half as Tabu's husband. Playing a supportive husband to an extremely talented actor like Tabu wasn't an easy job but SRK stood his own ground with his restrained performance. His pairing with Tabu was appreciated a lot, but sadly we still haven't seen them do a feature film together.
Bhootnath
In Bhootnath, Shah Rukh had an extended appearance as the film's child lead Banku. He played an engineer on a cruise line, and was only seen in a few scenes. He played a doting father to his son and had to support the Ghost (Amitabh Bachchan) to attain freedom. The film was a decent success, and much of it was thanks to Aman Siddiqui (Banku) and Amitabh Bachchan's crackling joyous chemistry.
Luck By Chance
SRK had only one scene in this film, but that was the one scene which stayed with you long after the film was over. He appeared as himself and delivered some words of advice for Farhan Akhtar's character which is essential for anyone who wants fame. It was felt by a lot of people, that the dialogues he mouthed were actually his own words.
57