Steel is a mixture of Iron, Carbon and other elements like Vanadium, Chromium, Nickel and even Phosphorus.
Solder is probably the next most used alloy. It is a mixture of Lead and Tin but can also contain Silver or Cadmium.
Aluminum is not usually an alloy unless it is used for a special purpose. Aluminum / Scandium alloys are used in aluminum objects which must be turned on a lathe. Pure Aluminum is too brittle to be lathed.
Copper is almost always used as a nearly pure metal. It must be 99.9% pure to have resistance low enough for wiring. Copper / Beryllium alloys have special properties which allow them to be used in plastic injection molds.
Precious metals are almost always alloys because Gold is softer than Lead and Silver, Platinum and Nickel can be used to make it harder.
A special alloy of Osmium and Iridium is used in ball point tips in pens. The osmiridium alloy is the densest and hardest of alloys and is plated on metal surfaces subject to heavy wear.