Antimony
It makes an alloy with lead. This alloy, 5% antimony and 95% lead, is harder than pure lead. It is used in lead acid batteries, as well as some other things. It is used  as an alloy with lead in the pipes of pipe organs. Pewter has antimony in it. Some lead-free solder has antimony in it. It is used as an alloy with lead in ammunition for small arms and in covering of cables as well. It is also used in some alloys that have very little friction like Babbitt metal.