Magic is often a game of tempo, making sure you can use what you play, not wasting a turn waiting. This is part of why Summoning Sickness is such a big deal, and why Haste is a well-liked ability.
Urabrask, The Hidden plays this to the extreme, making sure that not only do your opponents lose their momentum and are not able to ambush anyone with creatures that weren’t there a turn earlier (such as with Kindred Charge). Urabrask also gives your own creatures Haste, so you can play creatures knowing they’ll be able to swing in on both the turn they come out, and potentially the next (since the new creatures will still be tapped).
Uphill Battle is an enchantment that has creatures enter tapped, but doesn’t affect your own. Much the same as Urabrask, but doesn’t give Haste.
Authority of the Consuls has your opponent’s creatures enter tapped, but also gives you one life for each. (Potentially nice with Akroan Horse style effects).
Imposing Sovereign has creatures of your opponents enter tapped, and is on a 2/1 Human body.
Kinjalli’s Sunwing follows the trend of this paragraph, having your opponent’s creatures enter tapped, and is on a 2/3 Flying Dinosaur.
Thalia, Heretic Cathar has not only creatures, but also nonbasic lands enter the battlefield tapped under your opponent’s control.
Root Maze is similar, but affects artifacts and (any) lands (not just your opponents control). Works well in a ramp, creature, or enchantment deck, so that you don’t lose much momentum to it. It’s also one of the reasons I really started looking for ways to counter strategies, because a friend got this after I was preferring an artifact deck for a while.
Manglehorn also has artifacts enter tapped, but only for your opponents. It may also destroy one target artifact.
Blind Obedience is for creatures and artifacts of your opponents, but also has extort, which can cause quite a stir at a Commander table.
Frozen Aether, Kismet, and Loxodon Gatekeeper are all the same ability, “Artifacts, creatures, and lands your opponents control enter the battlefield tapped,“ which can severely lock down an opponent. Frozen is a color-shift of Kismet, and Loxodon Gatekeeper is just on a creature.
Due Respect has all permanents enter the battlefield tapped for one turn. This does affect you, but potentially could be played after you’ve done what you wanted, so that if an opponent is doing something at instant speed, this resolves first and their permanents enter tapped.
Last but not least, Orb of Dreams. This card can definitely be a stumbling block to decks that are all about tempo. But, if you’re deckbuilding with this and you have a way to find artifacts, you may want an Amulet of Vigor so you don’t have to punish yourself by dealing with the consequences of your actions.
Amulet of Vigor is also a great card to play if your opponents are playing any of the previous cards mentioned with these style abilities.
