Noble gases are unreactive. They do not ionize, and thus can't react. (Well, this is the case for Helium / Neon / Argon. Some krypton and xenon compounds can form, such as xenon trifluoride, xenon(VIII) oxide, etc).
All alkali metals (metals with a 1+ charge, group IA of the periodic table) react very violently with water to produce a metal oxide and hydrogen gas. The heavier they get, the more energetic the reaction is. (ex. lithium and water fizz a little, sodium + water is a bit more energetic, and potassium + water burst into flame and make loud pops).
Also, the halogens (1- charge, group VIIB, second to last group of the periodic table) are actually quite reactive (sorry lordly_dragon). Fluorine is the most reactive of the halogens. It and chlorine are very poisonous in elemental, gaseous form. They are corrosive gases. Bromine is also very poisonous in elemental form, it being a liquid at room temp.
Dissolved fluorine compounds are added to drinking water as well as toothpaste (such as sodium fluoride, this is the active ingredient in toothpaste), as the tooth enamel is much stronger if it becomes impregnated with fluorine ions.
Chlorine gas is also very corrosive, it causes irritation if it gets into your eyes and is poisonous inhaled. It is yellow green. In swimming pools it is usually in compound or in very low elemental concentration.
Anyway, to get everyone back to the topic, there are more useful reactions than alkali metal + water out there.
One such reaction I can think of is the thermite reaction. Try this sometime if you're bored (wear safety protection, I'm not responsible if you try this and get hurt. Do so at your own risk). If you do the thermite reaction with large amounts of reactants, you should be doing this under a fume hood, standing back, behind a blast shield.
The thermite reaction is the reaction between iron(III) oxide (otherwise known as rust) and aluminum metal, to produce molten iron, shown in the reaction
Fe2O3 (s) + Al (s) -> Al2O3 (s) + Fe(l)
Heat of rxn = -847.6 kJ (Pretty energetic)
Usually the reaction is performed with large amounts of powdered reactants and with several catalysts (I won't go into details, if you're really interested, google it) but you can perform the reaction with two rusty ball bearings and aluminum foil (or some other source of rust and aluminum).
Wrap one of the rusty balls with aluminum foil, so no rust is showing.
You should have a uncovered rusty ball as well as a ball covered in aluminum foil.
Wearing gloves (and other precautions, such as safety goggles), hold a ball in each hand and hit the balls together as hard as you can. You should get a flash, and a loud pop. If nothing happens, try again. You need to use sufficient force.
Again other sources are possible, you just need to be able to produce the activation energy required to react the metals together.
The thermite reaction is used in making explosives (the molten iron can melt down an engine block) as well as underwater welding.
Have fun!