If hitting hard with little red creatures is what you're up for, then Goblins is right up your alley
For gifts especially, receiving a card already inside a quality case makes a noticeably stronger impression than getting a card loose in a paper envelope
However, an older card such as a Pokmon which has the same name, but not the same stats and abilities (for example, the Sableye shown in the image above), would not be legal to include alongside a Sableye with the currently legal regulation mark
Some great cards and damage multipliers in this category are enchantments like Fiery Emancipation, Burning Earth, and War's Toll
Although acorns may feel like a random choice to denote a formerly silver-bordered card, squirrels have been the unofficial mascot of Un-sets