Today's New/Indie Gem Promo is the MSX-hard Metroidvania game La-Mulana
for 60% off. However, that's not the end of the update! GOG has launched a new "buy bundle" feature on their store, where you can get a discount on certain games by buying all the games in the franchise! As of right now, the following game series have discounted bundles associated with them:
Alone in the Dark
Little Big Adventure
Wadjet Eye Adventures
Sam & Max Series
Simon the Sorcerer
There doesn't seem to be any rhyme or reason as to what the sale price is for each series, however that may change if and when this feature leaves beta. Also, a cool feature of these bundles is that, if you already own some games in the bundle, you can buy the rest of the bundle at an even more reduced price.