As other people have said, first thing is to make sure you're travelling with people who know what they're doing and have the right gear for the trip. If there are inexperienced people coming along then you should be proactive about helping them. Ask them in advance whether they've got whatever you consider necessary for the trip, and if they don't then tell them they've got to get it before they come along.
Obviously there are some situations where you find yourself in the company of people you didn't have the chance to check out before the trip. In that case, if you really don't want to lend someone something the best solution is to ask what they need it for, and then help them with whatever task it is yourself. If its something that you need for yourself and you only have one of, like a rain jacket or limited fuel etc., then the best response is the honest one ie. "sorry mate, I've only got one and I need it."
The thing I don't do is just say "No" or come up with smartarse lines which leave a bad atmosphere and create tension in the group. The person asking you may be a complete dickhead etc., but can you be absolutely sure you may not end up relying on that person for something in the future? As unlikely as it may seem at the time when some unprepared person is asking to borrow your knife, matches etc., you may end up needing that person's help and if you've pissed them off unneccesarily by being a jerk they'll be that much less likely to give you the help you need. Doesn't mean you hand out your vital equipment, but you shouldn't be a jerk about it when you refuse either.
Obviously there are some situations where you find yourself in the company of people you didn't have the chance to check out before the trip. In that case, if you really don't want to lend someone something the best solution is to ask what they need it for, and then help them with whatever task it is yourself. If its something that you need for yourself and you only have one of, like a rain jacket or limited fuel etc., then the best response is the honest one ie. "sorry mate, I've only got one and I need it."
The thing I don't do is just say "No" or come up with smartarse lines which leave a bad atmosphere and create tension in the group. The person asking you may be a complete dickhead etc., but can you be absolutely sure you may not end up relying on that person for something in the future? As unlikely as it may seem at the time when some unprepared person is asking to borrow your knife, matches etc., you may end up needing that person's help and if you've pissed them off unneccesarily by being a jerk they'll be that much less likely to give you the help you need. Doesn't mean you hand out your vital equipment, but you shouldn't be a jerk about it when you refuse either.