I travel extensively throughout the world and have experienced my hand luggage getting weighed on multiple occasions. I'm a scuba diver and underwater photographer so I end up carrying on about 50 lbs worth of gear in hand luggage even though there is typically a 7kg weight limit. I'm usually traveling to remote parts of the planet and want to make sure my gear arrives with me. I couldn't care less if my clothes don't make it but my $15K worth of camera gear I don't want to put in checked luggage.
Here are some of the tricks I use:
- First, they typically only weigh the hand luggage at check-in and then give you a tag to put on your carry on bags showing that the bag has met the weight limit. I usually empty out my bag and leave all the heavy stuff with a friend or fellow traveler while I go check in. My bag is weighed, I get the tag and then I go back to put all of my heavy camera gear back in the bag.
- Second, I travel with a photo or fishing vest with lots of pockets. It's amazing how much gear you can stuff into the pockets. I try to fill these pockets with most of my heavy lenses, camera bodies, etc., so even if my bags do get weighed again while boarding the plane, the majority of the gear is on my body and not in the bag. Once I've boarded the plane, I put the gear back in the bag. I've only been pulled aside once to have my bag weighed before I boarded the plane and that was on a flight from Adelaide to Port Lincoln on a very small plane with only 5 seats.
The main trick is to make it look like the bag you are carrying is light. As long as it's the right size and you aren't struggling, you'll be fine.
The airlines that have given me the biggest trouble are Monarch (in the UK), Fiji Airways, Air Niugini and Real Tonga.
Good luck!