DominionStrategy Wiki
"Each other player shuffles their deck" would be an interesting mild attack on a card whose non-attack effect is some kind of deck-stacking (e.g. "Draw 2 extra cards during Clean-up, then put two cards from your hand onto your deck in any order.").
Knowing what's in your opponent's hand makes all the difference in end game tactics
The player -- is hurt more.
Bomb, Cannon, and many of the Gunpowder cards can strongly effect gameplay, particularly in a destructive way
If I were to tweak Sentry, I'd probably try a version that only trashed one card. Maybe only discarded one card too, for simplicity. "Look at the top 2 cards of your deck. You may trash one. You may discard one. Put the rest back in any order." Make it less swingy, you know? If the resulting card was too weak, I'd try "Look at the top 3 cards of your deck…"
pacovf has a neopets account. It has 999 hours logged. All his neopets are named "Jessica". I guess that must be his ex.