I'm sure this has been done to death before, however.....
Rootling through the garage looking for something else, I came across a box of stuff 'acquired' from a skip at a disused TV studio I was guarding. The stuff was mainly from the make-up & wardrobe depts.
While I'm sure a 100m roll of Wundaweb will come in handy one day I thought that these lead hem weights would make good boat ballast. OK not a massive amount of them but they would be good for fine tuning I reckon. They are 19, 13 & 7g, nearly 500g of them, OK they won't do anything that wheel weights don't but just different.
Also in the bag were about 10 of the magnetic fasteners shown. Cabin magnets now methinks.