Squidge

Squidge was a chemical compound which made things bounce "ten times as high as rubber". Its inventor — a professor whose name the Second Doctor, John and Gillian never knew — also claimed "you [could] do anything with it". He demonstrated that squidge could be used to make trampolines and highly effective weapons. When combined with a secret green chemical that removed elasticity, squidge produced super-strong yet super-light clubs. The professor's so-called "squidge clubs" made an excellent defence against sabre-toothed gorillas because of their highly manageable mass. Squidge was even used to make range weapons, such as the Doctor's "squidge catapult" — essentially a rubber band stretched between two trees. Its greater elasticity allowed for its ammunition to be discharged at extremely high and damaging speeds. (TVC: The Sabre-Toothed Gorillas)