Here's my Lua script to make BLLT from ELEC. BLLT will appear in the "explosives" menu because it explodes after it runs out of "Life". It also can electrify metal or other conductors when the ring of LIGH (the edge of the ball lightning) touches the conductor. The explosion does a decent ammount of damage.

Lua code:
tpt.el.elec.menusection=3
tpt.el.elec.color=0x9555ff
tpt.el.elec.description="Ball Lightning. Travels in strait lines and bounces of solids. It electrifies conductors. Explodes when Life=1."
tpt.el.elec.name="BLLT"
math.randomseed(os.time())
function ball_lightning(i,x,y,s,n)
if tpt.get_property("tmp",i)==0 then
tpt.set_property("life",math.random(50,150),i)
tpt.set_property("tmp",1,i)
end
for n = 1,50 do
xoff=math.random(-7,7)
yoff=math.sqrt((49)-(xoff^2))
if tpt.get_property("type",x+xoff,y+yoff)==0 then
tpt.create(x+xoff,y+yoff,"ligh")
tpt.set_property("life",4,x+xoff,y+yoff)
tpt.set_property("tmp",math.atan2(-yoff,xoff)/3.14159*180,x+xoff,y+yoff)
tpt.set_property("tmp2",1,x+xoff,y+yoff)
end
if tpt.get_property("type",x-xoff,y-yoff)==0 then
tpt.create(x-xoff,y-yoff,"ligh")
tpt.set_property("life",4,x-xoff,y-yoff)
tpt.set_property("tmp",math.atan2(yoff,-xoff)/3.14159*180,x-xoff,y-yoff)
tpt.set_property("tmp2",1,x-xoff,y-yoff)
end
end
if tpt.get_property("life",i)==1 then
for yoff=-38,38 do
for xoff=-math.sqrt((38^2)-(yoff^2)),math.sqrt((38^2)-(yoff^2)) do
if (x+xoff)>3 and (x+xoff)<608 and (y+yoff)>3 and (y+yoff)<380 then<br/> if tpt.get_property("type",x+xoff,y+yoff)==0 then
tpt.create(x+xoff,y+yoff,"plsm")
tpt.set_property("life",30,x+xoff,y+yoff)
tpt.set_pressure((x+xoff)/4,(y+yoff)/4,1,1,10)
end
end
end
end
tpt.delete(i)
end
end
tpt.element_func(ball_lightning,tpt.el.elec.id,1)