There are infinite combos that outright win you the game, like with Walking Ballista, but Heliod can be a centerpiece of devotion decks, +1/+1 counters, lifegain decks, and enchantment-based decks
Madison Li Dragon Breath Dragon Fangs Dragon Scales Dragon Wings Dreams of the Dead Drownyard Temple Eiganjo Dynastorian Elspeth Conquers Death Emerge from the Cocoon Emeria, the Sky Ruin
Song of the Dryads, one of the best green removal spells, and Lignify are similarly strong for this slot
Selvala's Stampede is only fun when you get to play mind games with the table and bluff that you have many more threats in your hand than you let on
(2004-10-04) Putting on a counter is optional
This quickly unlocks descend for Wail of the Forgotten and, even more importantly, can enable Kiora to create an 8/8 Scion of the Deep token as early as turn four