pack rat, scavenger, magpie - someone who collects things that have been discarded by others

miser - a stingy hoarder of money and possessions (often living miserably)

niggard, scrooge, skinflint, churl - a selfish person who is unwilling to give or spend

penny pincher - someone who is excessively careful with money (who pinches every penny before letting go of it)

saver - someone who saves (especially money)