As a gamer on a budget (aren't we all!) I've learned to hold on to "extras" or left over parts and use them for other projects.
The Disintegration Gun was built from and extra weapon from a Tau vehicle from Games Workshops Warhammer 40K, an extra landing gear, a leftover flying stand, 4 round plastic shields and extra copper wire from the shop.
The Cult of Doom (or any Adventuring Company) Arc cannon was made with extra wagon wheels, another Tau landing gear, an Elder Titan canon from Space Marine and some metal left over from weapon sprues for spears from North Star.
Objective markers: I use the following mostly as objective markers or treasure for In Her Majesty's Name.