For one man, there's no such thing as having too many consoles; which is why the Xbox Addict user hellon earth159 currently has 20 Xbox 360 systems sitting on his shelf.
Just think of all the co-op possibilities. Four player co-op system link Rainbow Six Vegas while also running another four player co-op system link session of Halo 3. And you still have 12 more consoles as backups!
Mr earth159 collects different style Xbox 360 consoles. Most of them are limited edition, some as rare as only 4 in existence! He usually scours EBay for this suckers, averaging about $1000 per console. Yes, that's 20 grand sitting on his shelf.
My personal favorite one is the Brother's In Arms: Hell's Highway one. Too bad they yanked the co-op in that.
Source: Hawtymcbloggy.com