Best buys? everything really... bought a cheap stinky, upgraded the parts, bought a cheap old banshee, put the old parts on it and sold it... made huge profit. then used that profit to buy my new banshee, put the new parts on it, sold the old frame. more profit.
bought a 2007 stuff for $100, dob frame for 300, upgraded and sold off parts. bike half paid for itself.
my best was trading my old jr.t for my current frame and shock (Rocky Mountain RM7fr)
my worst which was actually good was my first bike (2002 Norco Fluid with fresh rebuild on everything, new tires, new juicy 5s, and a few aftermarket bits) I paid 800 for it and later sold it with hayes 9s for 565
Worst: '08 Bighit stock. i thought it was nice, until i took it up to northtsar. i have upgraded literally every single component except for the cranks and rear shock
worst:dabomb dirt reaper tyres fine up until you show them the wet or slighly damp coditions best:specialized lo pro mag 2 pedals they are awesome like glue made me hate my v8s