Montreal Wanderers........
Depends on what you're looking for and what you're willing to spend. I have (or had) a pair of gloves and pants (of shell) from every current (or nearly current) NHL team at one point or another.
One team that sticks out in my mind are the Avs. Colorado Socks and 3.0 Practice jerseys are hard to come by for a reasonable price.
I have (or have had) a 3.0 practice jersey from every time except Phoenix, NYR, NJD, Colorado and StL. Colorado and StL are the two I haven't actually seen. I've passed on others due to price.
Tracking down full sets of WC or SS gear was also mostly successful. Just took time and money.
I'd say Pittsburgh is the easiest. Phoenix and LA are also pretty easy, as all those teams have sellers who dump a lot of it on ebay.