Only a few have single rider lines, but all other thrill rides will allow you to do Rider Switch if you are travelling with small kids.
Essentially one of you will wait in the regular line and you will be given a Rider Switch pass. Once the first person has waited in the regular line and ridden the ride, the second one will show the Rider Switch pass at the FastPass+ return line and will get to go in that much shorter line. You can use the Rider Switch pass anytime that day, so the person staying with the kids doesn't have to sit around and wait for the person waiting in line to be done. You can go off an do other things with the kids and then come back and use the Rider Switch pass later.
Here are the list of attractions which offer rider switch:
Magic Kingdom Park
Big Thunder Mountain Railroad
Splash Mountain
The Barnstormer
Space Mountain
Stitch’s Great Escape
Tomorrowland Indy Speedway
Epcot
Mission: SPACE
Soarin'
Test Track
Disney’s Hollywood Studios
Rock ’n’ Roller Coaster Starring Aerosmith
Star Tours® - The Adventures Continue
Twilight Zone Tower of Terror
Disney’s Animal Kingdom Park
DINOSAUR
Expedition Everest - Legend of the Forbidden Mountain®
Kali River Rapids
Primeval Whirl
This is from the official Disney World website which has further information:
https://disneyworld.disney.go.com/guest-services/rider-switch/#