@Datsun310guy well I least have a Datsun to justify all the Datsun parts in the garage. I've got 4 full gaskets sets, plus a bag with about two dozen water pump gaskets, oil pump gaskets, thermostat gaskets. A set of factory A12 flat top pistons, 76.5 mm forged pistons, A12A .20 piston set, 2 new oil pumps, oil pump rebuild kit, 2 sets of A12A piston rings, 3 sets of A14 pistons, 3 short blocks (A15 A12A A12), GX head, H72 head, electromotive cam, 24 36mm intake valves, 24 29mm exhaust valves, full set of 37/30 SI valves, set of Isky dual valves springs, 63 series 5 speed, auto bellhousing, 3 B210 fan shrouds, two pairs of 1200 doors, 1200 hood, set of 1200 bumpers, two 1200 coupe rear windows. This is after I just spent 6 months clearing stuff out, I got rid of a close ratio 4 speed plus 2 gear sets, GX radiator, GX valve springs, and a set of 74mm flat top pistons.
As for collections of stuff:
I've got model trains, a set of Lionel and various HO trains from my childhood. One of the spare bedrooms has a small HO layout.
Racing / automotive / motorcycle books. I was given some really cool stuff from a friend's father like the full set of the encyclopedia of motorcycles. When our friend Nick Strine passed his wife gave me some of his books; a Lauda bio signed by the man himself as well as signed Fast Guys Rich guys. Also have 80s Motocourse.
Race posters: My wife is a graphic artist and has the ability to laminate them. I've got a Japanese F3000 poster, framed Ceasers Place GP (was hung in the lobby and a sale guy new I was a racing nut, the casino was cleaning out stuff). 4 times Indy winners, autographed Subaru rally poster (Solberg), California 500, Los Angeles GP and Coys Historic Festival. These are hung in the garagemahal along with some vintage MX gear.
I never intended to but ended up with some cool race apparel from the 70s and 80s; Datsun Racingjacket , Brabham F1 jacket, Japanese F3000 team jacket and Prix Edition jacket with a bunch of really cool patches on it, New Ferrari F1 jacket, 70s Honda bike racing T-shirt, unopened Kenny Roberts race T-shirt, vintage Yamaha MX jersey, Isle of Man jersey and 80s Honda T with kanji letters on it.
I never set out to have a collection so I just have a mish mash of stuff poeple gave me or things I find cool. Fortunately none has any big value so I'm not tempted to sell any of it.