If you're a traveller or visitor to the city of Kuala Lumpur, you can purchase RapidKL MyCity Day Pass. It allows unlimited rides on LRT/MRT/BRT/Monorail for 1 -3 days.
1 Day Pass costs only RM 25 while 3 Day pass costs RM55. This pass can be purchased at all rail stations LRT/MRT/BRT/Monorail. The only thing it doesn't cover is the RapidKL bus fares.
This pass can be said equivalent to Hong Kong's Octopus card 八达通, a daily unlimited rides pass for travellers.
More info can visit RapidKL's official website on this.