Beyond this the synergies are subtle and tend to only involve a few cards, for example Chandra's Phoenix improves Lava Dart, the few creature pump effects improve Spikeshot Elder, Mogg Fanatic and other creature sacrifice effects improve Brimstone Volley and the things that give haste work really well with Keldon Marauders
You can also pour infinite mana through Memnarch to take everything your opponents own
Niche cases, sure, but they will happen
Shadow of the Second Sun is huge here, as you can get your commanders benefit right after casting the Shadow, as is Portal to Phyrexia to undo whatever benefits your opponents obtained
What I really like is that theres no alternative casting cost, so you can use this mana to pay for an overloaded spell
Niko, Light of Hope Niko, Light of Hope is a 2/3 human wizard that already makes two Shards, which are upgraded enchantment Clue tokens