Dr. Mario (SSB4)/Up aerial
Dr. Mario performs a bicycle kick. While similar in animation and frame data to Mario's up aerial, the different angle makes the move much different. The angle is more horizontal rather than vertical, which alters its combo ability. It can still combo into itself, neutral aerial, jab, grab or tilts at low percents, alongside back aerial with the back hit of up aerial, but its most notable use is up aerial to Super Jump Punch, as up aerial launches perfectly for the attack to be combo'd into. The unique angle also makes it somewhat useful in edgeguards, and the move can be used twice in a single short hop if both are buffered. The fast startup allows the move to effectively break combos as well.
Overall, a very useful part of Dr. Mario's kit, notably due to its combo ability and generally low lag overall.