Really great for Zoey Samaras:

• boosts her fight,
• boosts her fight with Wither / Spectral Razor / ... if there is a Creature / Monster at the location,
• you spare the action to engage the enemy (if it is engaged with an other investigator) and get an auto-damage with Zoey's Cross,
• gives your the last move you need to enter the location of the enemy Smite the Wicked is attached to.

At 2+ player you can also ask a seeker to play Existential Riddle on a Creature / Monster hunter enemy so that you have the double bonus all the time (as long as you move only one location perround).

Note that Handcuffs can potentially make this ally really effective by attaching to an enemy that also has the Humanoid trait.

This is very common in the Innsmouth Conspiracy campaign, and also weaknesses like Yorick’s Graveyard Ghouls can even put one in your player deck.

In 3~4 players where one of you is likely getting an enemy, I've repeatedly benefited from engage. It's great even when you are not getting any free move out of it but even better if you could and want to move there anyway. You can strategically spend your action for something else and stay behind on purpose expecting that your bigger group will draw at least an enemy for you to move to.

The has a few more tricks that let you move even more than you're supposed to, you can utilize Hunter enemy's move (to other players) to stretch the distance by triggering in the Enemy Phase. You do have to engage it and take the hit, but maybe you can save someone else from getting hit doing that.

In Mythos Phase, if prior player nearby draws an enemy and you draws a test, you can even move before the test in order to get their commits and maybe additional +1 if enemy is Creature or Monster.