A surprising Community fan theory may explain why Pierce didn't bequeath a personalized gift onto Abed after he passed away as he did for everyone else. Community season 5, episode 4, "Cooperative Polygraphy," is a bottle episode that features the gang gathering in the study room after Pierce's funeral. There, they are greeted by Pierce's executor (Walton Goggins) who makes them all undergo a polygraph test in order to determine whether any member of the group murdered him, as per the wishes expressed in Pierce's will. At the end of the session, everyone except for Abed receives a special gift (as well as frozen samples of Pierce's semen). The will states that "nothing you ever said made any sense to me."
Community is known for its self-aware, meta-comedy. It's even been theorized that the study group's empty chair is for the audience. By far the most self-referential character in the Community is Abed Nadir who spends most of his time commenting on the events taking place, applying popular media tropes and narrative structures to the humorous situations the group finds itself in. The other characters often feel alienated by Abed's incessant references to popular movies and tv shows; Pierce, especially, is always confused by Abed's eccentricities.
Reddit user, EquivalentInflation, suggests that Pierce did, in fact, offer Abed a personalized gift: the episode itself. Pierce's lie detector creates a situation in which all of the characters have their worst secrets exposed, thus creating drama within the group. This kind of manipulation is something Abed has been known to do before; in fact, in this very episode, it is revealed that he has been tracking every other member of the group. Abed probably knows he's on a tv show, which is why he enjoys when situations play out in accordance with certain dramatic rules. Indeed, Abed immediately catches onto the episode's dramatic structure. When confronted with the saddening truth that Troy actually copied their signature handshake from a YouTube video, Abed even comments: "I forgive you, but only to escape the established pattern of self-righteous indignation followed by immediate comeuppance," and when Goggins' character proceeds to reveal one of Abed's own secrets, Abed remarks "Okay, I guess it's happening anyways."
While this episode of Community ends on a rather melancholy note, with Troy accepting Pierce's condition that he sail around the world in order to receive Pierce's shares in the company (meaning Troy will exit Community), Abed later overcomes his ambivalence towards his best friend's departure in the following episode, season 5, episode 4, "Geothermal Escapism." Thus, Pierce's gift to Troy provided character growth to both Troy and Abed. Troy makes an important choice about his future and Abed learns to let his friend go and become the man he wants to be.
However, it's also possible that Pierce genuinely didn't know what to get Abed, meaning he never truly understood him right up until the very end. No matter what the case may be, Pierce did, intentionally or unintentionally, provide Abed with the perfect parting gift: a meta exploration of the characters that provided him with the opportunity to comment on the nature of the show. In doing so, Pierce turned his own death into a brilliant episode of Community.