They provide a variety of booster packs, tins, and collector's boxes
Using a microscope or magnifier, you may find out that the original card has a multi-layered print
Once per turn, if this card has a Trap as material (Quick Effect): You can detach 1 material from this card, then target 1 card on the field
This means that to Link Summon LANphorhynchus you just need to send any two monsters you control to the Graveyard as Link Material (similar to a Synchro Summon, but in this case you don't need to meet any Level requirements)
It also usually grants some other kind of benefit, which leads to some interesting designs that pair the counters with the front side of the cards
The Mega Tokyo's Pikachu promo is actually a reprint of Mega Tokyo's Pikachu 098/XY-P with new artwork