A man who didn't realise it was illegal to carry the taser his mate bought off discount website Wish told police he "thought it would be cool".
Police intercepted Malcom Harkin, 33, on Melrose Drive, Wodonga last year at 2am.
Wodonga Magistrates Court heard on Tuesday that Harkin's car had been searched by police who found a black case under the driver's seat.
"In the case officers found one CED device, or a taser, and two cartridges," police prosecutor Leading Senior Constable Penny Lawler said.
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"The accused declined to answer any questions, but said he didn't realise it was a prohibited weapon."
The court heard Harkin bought the taser from a friend who had purchased it through Wish and it was an "error of judgement".
Magistrate Peter Mithen convicted him and fined him $500.
The weapon was seized and destroyed.