Yep, I've heard of people stacking as these are 'gift cards' and not codes.
Just FYI, here are some coupon codes with NO minimum purchase (to use if your order totals to <$25)
fullaction: receive a free SEPHORA COLLECTION Full Action Mascara deluxe sample (0.10 oz)
skinstars: seven free skincare foil samples.
MS2U8E: Shiseido Urban Environment Oil-Free UV Protector SPF 42
MT34S7: 0.3 oz Tarte Smooth Operator™ Amazonian Clay Illuminating Serum
agedefy: receive a free Sephora Collection Age Defy Moisture Cream SPF 15 0.169 oz
trybuxom: receive a Buxom Lash Mascara deluxe sample (0.2 oz), free with your online merchandise
3stepdry: foil samples of Clinique's 3-step skin care system for dry skin
blisspeel: Bliss That's Incredi-‘Peel’! Spa-Strength Glycolic Resurfacing Pads
These codes can only be used online correct?