If you happen to be lucky enough to live along the coastal area than the perfect job for you as a girl or guy would be a lifeguard. As far as summer jobs for 14 year olds, being a lifeguard ranks as probably one of the best jobs that you can get not only because you work in a very fun atmosphere but you also learn how to be responsible, because when you are out there at the beach many people's lives are in your hands.
In order to become a lifeguard you have to take a certification course, plus you also need to prove that you are a more than adequate swimmer. As far as how much you would get paid as a lifeguard it all depends on the state that you live in and whether your area is saturated with lifeguards or not, but generally the range of pay for lifeguards starts at minimum wage and goes all the way up to $20 an hour, but like I said again you need to do some homework and ask around about the pay in your area, but if you're looking for a great job in which you mostly sit around all day and get a great tan than being a lifeguard is just the thing for you.
Yard work, small jobs like pulling weeds or clearing out dead flowers, is always good. Sell yourself to people on this by telling them you only do the smaller things, stuff professional landscapers charge big bucks for, break it up by the job...find out exactly what they need done (esp if you are not knowledgable in yw...don't want to pull up a flower thinking it is a weed) and go from there. Not knowing where you live, the only thing I can add it baby sitting, and life guarding at your local pool (has some requirements however, check these out first, but pays really well at a country club or neighborhood pool.)
Babysitting. If you don't mind doing it at the last minute sometimes? And parents need them a lot on weekends! I made fantastic money in my teens. Plus you dictate what the pay will be. Your the one getting hired! Don't watch 3 kids for 8 hours for 20 dollars, is all I'm saying. I would charge 2.00 a kid an hour? So 3 kids for 5 hours = 30.00 dollars. Remember I got this pay in the late 80's??? So a little more would be appropriate. Also always get paid in cash when they get home!!! A must! Good Luck! :-)