I usually boil tea water on…

• Outdoor fire
• Hearth
• Stove burning room pressure liquid
• Primus stove
• Stove with LPG cylinder
• Stove with municipal gas
• Submerged water boiler
• Electric stove
• Induction stove
• Water boiler
• Electric kettle
• Coffee machine
• Microwave oven
• Vending machine
• Central heating
• Solar hot water panels
• Oven
• Geyser or natural hot water springs
• Car engine
• Computer processor or video card
• Lens collecting sunlight
• Nuclear reactor
• Volcano
• Breathing fire
• I make tea from cold water
• I buy tea
• I never drink or make tea

I guess this is too long as well. Should try to find a way to make it shorter. Or find a place for longer polls.

Update: added Geyser or natural hot water springs.

Update 2013-02-16: done at I usually boil water for tea using a(n) ....