A/C Recharge
I have a 2002 Nissan Sentra GXE that was built in 2001, and I have owned it since it was new. I have never had to add refrigerant to the system yet; and I hope it can get through this summer as well.
If not, Wal-Mart sells a can of refrigerant (R-134a) with the little hose/cap attached to it - for about twenty bucks.
P.S. If your car is pre-'94 and has not been retrofitted, you will probably have to use the old R-12 (Freon); which is very hard to find.