An Overwatch player has discovered a method for boosting Sigma's jumps using his primary fire weapon, allowing the tank to tank otherwise unreachable positions.
To execute the jump trick requires manipulating Sigma's Hyperspheres such that they detonate just below his bare feet, giving him a brief extra moment of hang time before he resumes falling. The boost is small, but in Toddeh_'s video it's enough to reach the raised platform beside the gate at Hanamura's first point, opening up the high ground position for the defending team.
Because Sigma is typically one of the least mobile heroes in Overwatch, this small increase in positioning options is significant. Exactly how useful it will prove remains to be seen, as implementing it in actual Overwatch play will take a substantial amount of experimentation and research.