These are just combos I like either for looks or for handling... feel free to share yours! :)
Master Cycle, Triforce wheels, Hylian Kite, Link- Because Zelda is like my favorite game series of course I love this combo!
Mr. Scooty, Azure Rollers, pretty much any kite, Dry Bones, Link, Toad, Toadette- Very good handling and acceleration, a combo used often in competitive
Biddy Buggy, azure rollers, that cloud glider thing (Forget it's name T-T), Dry Bones- Very good accel and handling, used a lot by people in competitive.
Flame Rider, retro off-road, bowser kite, Bowser or Dry Bowser- Matching combo with the character, and it looks good!
Standard Kart, Standard tires, Standard kite, Mario, Yoshi, or Luigi- Good speed, good accel, good handling. Starting to be used by a lot of people in competitive.
Varmint, Roller, Paper kite, DK, Mii, Link- Good speed, accel, handling.
Jet bike, azure rollers, Plane glider- Looks nice, I remember when this was the best combo in MK8 for Wii U.
Yoshi bike, rollers, Hylian kite- I just like it, it is cute and I like the looks.