WEB PAGES: Female, because they're constantly being looked at and frequently getting hit on.
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TRAINS: Male, because they use the same old lines for picking up people.
EGG TIMERS: Egg timers are female because, over time, all the weight shifts to the bottom..
HAMMERS: Male, because in the last 5000 years, they've hardly changed at all, and are occasionally handy to have around.