Here are some tools that you may need for future installations.
Strippers: Used to remove insulation from wires. $15-$20
Crimpers: A basic tool all installers should have. ($15 - $30)
Fish wire: A piece of home electrical solid core wire (insulated). Cut in different lengths, it can be used to pull wires under carpet and through firewalls. Price: $1 - $2.
Soldering gun: Can also be used for "plastic surgery" (melting plastic) and heating up metals. It is highly recommended that you spend the extra money and get a high powered model (100W and above) $30 - $50
Mechanics tool set: needed to remove screws, nuts, bolts, etc. $50 up to $1000
Angled screwdrivers: Ideal for getting in tight corners, where normal screwdrivers will not fit $30
Door handle clip remover: Usually a piece of flat metal with an open hole that goes behind the window crank and pushes the clip out. Cost: $15 - $25. Available at car parts stores and specialty tool stores.
Panel removal tool: A mutation of a screwdriver, fork and pry bar, used to remove panels, and pulling snaps off. $15 - $20.
Drill: Used for audio and security installation. $40 and up.
Knives: basic utility knife and carpet knives are a must have for any installer. ($10 - $20)
Dremel tool: A rotary tool that has many attachments used to cut, polish and grind metal, wood, plastic, etc. $50 - $60.
Hot glue gun: Electric or battery powered. $10 - $30