Drug laws
Trafficking above threshold quantities carries a mandatory death sentence, and executions take place. The thresholds are low — 15 grams of heroin, 500 grams of cannabis — and possession alone carries long imprisonment and caning.
Singapore also prosecutes consumption. Authorities can require a urine test on arrival, and testing positive for drugs consumed abroad before entering is an offence. This applies to substances that were legal where you took them.
The rules people actually fall foul of
Vaping is the big one: e-cigarettes are banned outright and cannot be imported, possessed or used. Devices are confiscated at the airport and fines are substantial. Chewing gum imports are restricted.
Also enforced: littering, jaywalking, smoking outside designated areas, eating or drinking on the MRT, and taking durian on public transport. Fines are issued to tourists as readily as to residents. Vandalism, including graffiti, carries caning.