Police are investigating the robbery, which happened at Glenferrie railway station about 8pm.
The bandit walked up to the 18-year-old victim and told him he would be bashed if he didn't hand over his cash.
The teen handed over his money and the man fled.
The victim was not injured in the incident.
Anyone with any information is asked to contact Crime Stopers on 1800 333 000 or www.crimestoppers.com.au.
The three victims, a 21-year-old and two 18-year-old males, were talking with friends outside the Edithbale Life Saving Club in Melbourne's southeast about 2am today.
The trio noticed several men sitting in a dark-coloured Holden sedan opposite the Edithvale Railway station.
About 20 minutes later, three men came up from the beach armed with metal bars and attacked the three friends outside the club.
The 21-year-old, from nearby Chelsea, was hospitalised with serious facial injuries, while an 18-year-old also from Chelsea and an 18-year-old from Hampton suffered less serious facial injuries.
The offenders also smashed the windows of the 21-year-old's car before fleeing along the Nepean Highway.
Police with to speak to the men who were sitting in the Holden.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000.
Police believe the attacked in Clayton was unprovoked, and are seeking witnesses to the assault that occurred outside a restaurant on Clayton Rd, near Haughton Rd, at 11.50pm.
The group are believed to be aged between 15 and 20 years, and one female was involved.
One man is believed to be African, and others in the group are Pacific Islanders and Caucasian.
A 30-year-old man from Clayton South had his forearm slashed in the attack and was taken to Monash Medical Centre for treatment.
Anyone with information should contact Crime Stoppers on 1800 333 000 or go to www.crimestoppers.com.au
The 31 year-old man from Coburg North was walking from a bar where he worked through a lane near Grosvenor St at 11.10pm when he was confronted by two men.
The men demanded money before punching the victim in the stomach. He ran to South Yarra station where he realised he had suffered a minor stab wound.
An ambulance was called after the victim got into a taxi and asked to go to the hospital.
He was taken to the Alfred Hospital after being treated by paramedics.
Anyone with information about the incident urged to contact Crime Stoppers on 1800 333 000.
It will be alleged that the woman drove a car at a 60-year-old man standing in the driveway, allegedly knocking him over.
It will also be alleged that she then stabbed a 50-year-old woman.
The man was treated at the scene; the 50-year-old woman was taken to the Princess Alexandra Hospital for treatment.
A 40-year-old woman from Forestdale has been charged with two counts of attempted murder and is to appear at the Ipswich Magistrates Court on Saturday.
Police were called to a property, near Wujal Wujal, about 150km north of Cairns, at 3.45pm on Friday.
Initial investigations indicate the woman was shot in the throat, police said.