Item-lines with above average power but have actives with long charge-up times would be interesting

Just to give an idea what I mean (you can probably come up with better ones), picture some kind of crossbow/gun item that has an active with a 10 second charge-up time that immobilizes your champion but when completed significantly increases the range of all your abilities and auto attacks for 10 seconds (effect is cancelled when a movement command is issued).

Or another item with a 20s charge-up time (does not immobilize your champion) and when activated your champion's attack speed is doubled for 7 seconds.

I'd like to hear any ideas you might have for items with higher than average power but have actives that require extra foresight and planning to make effective use of. Can you think of any that might work for melee champions?