Luigi (SSBU)/Up tilt
Luigi performs an uppercut while jumping. It is a useful combo starter, however at very early percents, it is unsafe on hit, so its combo potential comes moreso from mid percents. Up tilt can notably lead into most of his aerials, itself (although not reliably), and even Super Jump Punch for a strong KO, or up aerial to back aerial for high damage and a potential kill at ledge. The higher speed of up tilt and being harder to DI can make it a more useful combo tool over down throw in situations where grabs are too slow or when it is possible to DI out of a Super Jump Punch KO. While it can work as an anti-air on shorter ranged landing options, the head intangibility and extra area coverage of up smash is better suited to this over up tilt.
Up Tilt is also useful as a way to shark platforms, being safer but less rewarding over up smash. It also hits quite low for an up tilt, allowing it to hit ledgehangs and even two-frame certain characters, allowing for slightly extended combos due to hitting opponents from a lower point. Aside from its confirms into Super Jump Punch, up tilt itself cannot kill well at realistic percents, although can kill earlier than up throw. It also cannot hit behind Luigi very well, if at all.