Let me throw in Parks408 and Parks409, as well as routes 36 and
925 - all four actually enter carparks along their routes.
Additionally, route 36 is weird for another thing - being the only
"infinite loop" bus route in Singapore 
.
But my votes still go to extreme circuitous routes, like 859
(WTF?!) and 123 (oh shi...), along with Express 518 (one gigantic
loop from PIE, down Orchard Road, through Suntec, up east along
ECP, and finally closing the loop at Bedok ), and the ones above.
Routes 5, 45, 175, and 185 are also rather weird - 45 and 185
ending at bus depots at one side, and routes 5 and 175 seemingly
loving to cut through "small alleyways" rather than use the main
corridors.
