The classic use for Phage is the one turn win method. Accelerators such as:

[[Dark Ritual]][[Lightning Greaves]]

Are absolutely necessary.

In addition: Phage's drawbacks make her difficult to play, but turn them into advantages by slinging her at your opponent!

[[Phage the Untouchable]][[Endless Whispers]]

Combining unblockability with a card similar to Whispers, your opponent gets to choose whether to lose or... lose.

Since you mention "memory", I remember that in the London prerelease for Legions, one kid was playing Phage the Untouchable and [[[Animal Magnetism]]] in the same deck... which really does seem to be asking for trouble!

[[Animal Magnetism]] [[Phage the Untouchable]]

For silly combos, it's quite hard to make Phage enter the battlefield under your opponent's control to kill an opponent with the "lose the game" trigger. Endless Whispers as mentioned by Shushoto is one of the best ways. Another, sillier, one: [[[Summoner's Egg]]] + Phage + a Donate effect such as [[[Bazaar Trader]]].

[[Summoner's Egg]] [[Donate]] [[Bazaar Trader]]