I do collect various odds and ends, but if it's diecast vehicles, then, I started collecting emergency vehicles, i.e. Police, Ambulance, Fire brigade, Coast Guard, etc etc, originally for my model railway.
But, since I have a layout no more, there isn't much need for them now
Thinking of selling some, but I'll keep some of the better and unusual ones.
Also I'm selling a lot of my trains, but again, I'll keep the really special ones, such as the Immaculate and mint in box, Wrenn, 8F, the Merseyrail Yellow '73, and 59003 in it's special DB livery, not to mention various other lovelies.