As mentioned, if not doing a lot of soldering, almost anything will work.. the one thing a lot of the soldering irons from radio shack dont have, is a lot of capacity. 25-40 watt irons dont do well soldering on wiring outdoors (unless light gauge). The just dont have the heat capacity.
the soldering equip I use is a 60 W station, with a relatively large tip. Lots of mass in the tip, it helps keep the temp up when you start to work. It is a temp controlled station, that I used regularly for soldering 1700 mah sub c nicads together using heavy (probably 8 gauge or larger) braided wire. Too bad the manufacturer of it is gone, as tips are no longer available for it.
Even a 40 watt iron will work for most stuff as long as the tip has enough mass so that it dont cool down the second you make contact with the items to be joined