Besides just during the attack phase, there are many different ways to forcibly tap your own creatures that are used to trigger any number of effects
Graded Population Report: Haunter #27 Visualize the distrbution of grades in the chart
When this card is Ritual Summoned: Halve the ATKs and negate the effects of all monsters your opponent controls
It seems usable for aiming for a one-shot kill by using it on [Tifa Lockhart], mentioned later
Ill focus on Commander, with a nod towards other formats where I think something deserves mention
Every time you activate the Venture keyword, which will appear on several cards in Adventures in the Forgotten Realms, you'll progress through a dungeon, exploring another room, and activating whatever ability is inside