emerson customs are good, onion, mayo, snody, also good, one thing is ya gotta get a good price on the things, if ya pay a premium from the get go ya rarely make anything on 'em, some disco'd spyderco's appreciate well, i bought 3 Ti ATR's a few yrs ago at about $150 ea. or so, they are worth a bit more than that now,
really, as far as investments go, knives a really pretty poor investments, most makers whos work appreciates well have long waiting lists (ie emerson, etc) so to get one ya already have to pay a premium, though they may stick in value from there they rarely go above it, unless the 'smith was to retire/pass away/etc, or ya win a lottery and get to buy an emerson at his MSRP, which is $550, then ya can double that right away, at least,
its just hard to tell whats gonna go way up, whats gonna stay where it is, and what might even fall in value, its a crap shoot.