There are several great single rider lines at Epic!
Monsters Unchained is a great time saver, but don't do it for your first time- You'll miss a lot of interesting queue and backstory. I've seen a 75 minute regular Q that dipped to 15 minutes on and off by going single rider line.
Mario Kart: Bowser's Challenge is a great time saver, again missing a lot of cool Q. The funny thing is the Express line here- not so great, dumps you into the main Q before you get your headpiece, and you still have to go down 3 flights of stairs while standing in line. Single is the middle row of the stairs, and you pass a LOT of people.
Stardust Racers has a single line Q, but I've never used it cuz it's hardly ever open. I've you time it right, you'll have an under 25 minute Q on Stardust several times a day, just be patient.
Curse of the Werewolf single line will average to about half the posted Q time- not bad.
Mine Cart Madness- honestly don't have much experience with. I can't stand in line for *anything* more than 30 minutes, (even at my new most beloved park

) so I've only done this ride at Early entry rope drop, or with an express pass.
Harry Potter: Ministry of Magic- there is a single rider line, but you can't do it your first time, or probably several times after that- the Q is just so Spectacular and mind-blowing! Pictures don't do it justice, it must be experienced to be believed. If you wait until the last couple hours of the day, you'll often have under 20 minute wait.
Hiccup's Wing Gliders- The single line moves almost the same as Curse of the Werewolf- not bad, half the time. I've noticed that ride times fluctuate wildly during the day in Isle of Berke, more than some of the other lands IMHO. I love this ride immensely, but I generally wait for under 30 Q time to head over there. The longest walk from Portal to Ride Q IMHO.
Have fun!
Rick