Since the other answers have been written, a card has been released that explicitly allows activating loyalty abilities any time you could play an instant: Teferi, Temporal Archmage from Commander 2014.
He's a planeswalker with a relevant ultimate:
−10: You get an emblem with "You may activate loyalty abilities of planeswalkers you control on any player'...
The rules for planeswalkers changed with the release of Ixalan on September 29, 2017, so the second part of this answer is no longer correct, but is left for posterity.
With the release of Ixalan all planeswalkers have the Legendary supertype (with all previous ones receiving errata to add it to existing cards), and the Planeswalker Uniqueness Rule has been ...
This doesn't work. The rule “you can’t attack something with flying” doesn't exist. It doesn't exist because you don't attack creatures: you just announce creatures as attacking a player or planeswalker, and then the defending player assigns blockers.
Flying only controls what can be declared as a blocker of that creature, and nothing else. Here's the rules ...
There used to be a long shot that could make this happen:
You start by playing the Mycosynth Lattice which turns all your permanents into artifacts, including planeswalkers.
Then you play March Of the Machines, turning your planeswalker into an artifact creature with power and toughness equal to its casting cost.
Then you use the ability of an Experiment ...
A planeswalker enters the battlefield with double the normal counters, but the counters gained or lost from activating one of its abilities are unchanged.
Doubling Season doubles the loyalty counters placed on a planeswalker entering the battlefield.
You've correctly identified the relevant rules.
From the comp rules:
306.5b A planeswalker is treated ...
Currently (in November 2018) there are the following sets of planeswalkers that you can use for your commanders:
The five double-faced transforming planeswalkers from Magic Origins. This is because they're a Legendary Creature on their front face, which is what the Commander rules are looking for.
Nicol Bolas, the Ravager, also a double faced card that ...
No, because even if it's not printed on the card, they're still Legendary due to errata:
306.4. Previously, planeswalkers were subject to a “planeswalker uniqueness rule” that stopped a player from controlling two planeswalkers of the same planeswalker type. This rule has been removed and planeswalker cards printed before this change have received errata ...
Planeswalkers are not players (or opponents), and they're never treated as players (or opponents). Don't think of them as players, and you'll be a lot less likely to get confused.
There's pretty much just a single rule that make them seem a little similar to players: you can choose to attack your opponent and/or planeswalkers they control.
Along with that, ...
Yes, a planeswalker will return as if you had just played it, with full loyalty counters.
Blinking a Planeswalker means to first exile it, which indeed removes all counters from it, and then returning it to the battlefield, with a number of loyalty counters on it equal to the loyalty printed on the card.
400.7. An object that moves from one zone to ...
Does excess Planeswalker damage hit the player?
An creature only deals damage to the player or planeswalker it is attacking. In this scenario, it must assign 5 damage to the planeswalker.
510.1b An unblocked creature assigns its combat damage to the player or planeswalker it’s attacking. If it isn’t currently attacking anything (if, for example, it ...
When you blink Garruk, the Veil-Cursed, it will return as Garruk Relentless as if you had just cast it.
When a permanent such as a planeswalker leaves the battlefield, it becomes a new object with no relation to its former existence. When it returns, it will enter the battlefield as if you had cast it from your hand, non-transformed and with full loyalty.
306.5d Each planeswalker has a number of loyalty abilities, which are activated abilities with loyalty symbols in their costs. Loyalty abilities follow special rules: A player may activate a loyalty ability of a permanent they control any time they have priority and the stack is empty during a main phase of their turn, but only if none of that permanent’s ...
No, this is not possible. The rules clearly state
903.5b Other than basic lands, each card in a Commander deck must have a different English name.
Since there are different Jace planeswalkers, you can include multiple of them, but you can only have one Jace Beleren.
You will gain life by attacking a planeswalker with a creature that has lifelink. More generally, any damage source with lifelink will cause you to gain life if it deals damage to anything.
The definition of lifelink in rule 702.15b says this:
Damage dealt by a source with lifelink causes that source’s controller, or its owner if it has no controller, to ...
Yes, after you choose which creatures are attacking, you may choose whether they are attacking the defending player or a planeswalker that player controls.
From the comprehensive rules:
508.1. First, the active player declares attackers. This turn-based action doesn't use the stack. To declare attackers, the active player
follows the steps below, in ...
This is covered by the Magic Comprehensive Rules:
121.1. A counter is a marker placed on an object or player that modifies its characteristics and/or
interacts with a rule, ability, or effect.
711.7. When a double-faced permanent transforms, it doesn‘t become a new object. Any effects that
applied to that permanent will continue to apply to it ...
The damage can't be prevented.
This is a situation covered by the second Golden Rule of the game.
101.2. When a rule or effect allows or directs something to happen, and another effect states that it can’t happen, the “can’t” effect takes precedence.
Example: If one effect reads “You may play an additional land this turn” and another reads “You can’t ...
Essentially, all cards that mention that "damage can't be prevented", though the sorceries will require additional cards to be cast during Gideon's owner's turn.
Those cards do what they say on the tin; damage can't be prevented, neither by activated abilities like Circle of Protection nor by static abilities like Gideon's.
You are not required to attack planeswalkers before the player.
When you attack, you may attack either the player or any planeswalker they control. The rules on declaring attackers quite simply state you choose attackers, then you choose which player or planeswalker each one is attacking:
508.1 First, the active player declares attackers. [...]
Lifelink is defined as follows:
702.15b Damage dealt by a source with lifelink causes that source’s controller, or its owner if it has no controller, to gain that much life (in addition to any other results that damage causes). See rule 119.3.
Attacking a Planeswalker deals damage to it.
510.1. First, the active player announces how each attacking ...
It's 'just' a regular Throne of Eldraine card, found in boosters and tournament packs – if you're lucky, of course; those cards are always random.
There is a preconstructed Throne of Eldraine deck with an Oko planeswalker, but it's Oko, the Trickster. You can find those decks e.g. here.
In general, Planeswalkers are slow to do anything by themselves, so the ones that see tournament play are the ones whose early abilities complement the deck or give immediate card advantage.
Gideon, Champion of Justice
Gideon takes about 4 turns to get out (by mana cost). His +1 doesn't do anything useful immediately, and even when he does get big he can ...
Yes, any target includes planewalkers
The wording was a relatively recent change. Previously, very few damage-dealing spells and abilities could target planeswalkers directly. Instead, you redirected damage from targeted players to one of their planeswalkers at resolution.
114.4. Some spells and abilities that refer to damage require “any target,” “...
Yes, No. Doubling Season does what it's errata says. If a Planeswalker would enter the battlefield with X counters, Doubling Season causes it to enter with 2x the number of counters. Loyalty abilities add counters, but these are a cost not an effect, so Doubling Season does not replace that.
Doubling Season affects cards that "enter the battlefield with" ...
You can have multiple planeswalkers in play as long as the card name is different. For example: Garruk, Cursed Huntsman and Garruk, Wildspeaker. I choose Garruk because of the new card from Throne of Eldraine: Garruk, Cursed Huntsman. His first ability says create 2 wolves with when a created wolf die you put a loyalty counter on every Garruk in play.
Disclaimer : I don't play standard, so if you look this from standard perspective, then it maybe somewhat irrelevant.
These are basic factors that should used when evaluating a planeswalker.
How efficient is the casting cost?
Can it protect itself and you?
How good is it assuming you can't fetch its ultimate?
How much the board impact it provides if you ...
Both the other answers quote a rule which tells you to look at 119.3, but fails to take a look at that rule. Rule 119.3 details what actually happens when damage is dealt. For instance, 119.3c says
Damage dealt to a planeswalker causes that many loyalty counters to be removed from that
And 119.3f says
Damage dealt by a source with ...
The steps to making Nicol Bolas a 4/4 "legendary artifact creature planeswalker" with a +1/+1 counter work fine, and you are correct that only creatures with flying and reach can block him if you attacked.
This is where it gets a little tricky, from knowledge there are no rules around attacking a planeswalker with flying, so I would suggest he can still be ...
I think a major element is that these planeswalkers all provide some form of card advantage the turn they come into play as a +1: card draw (Domri and Garruk, caller of beast's +1s fall in that category), tokens, mana, discard... Planeswalkers that majorly hobble the opponent with their +1 (Jace Architect. Kiora) are also playable. The major exception is ...
A Planeswalker is never a player. Spells that target a player can't target a planeswalker.
However, noncombat damage can be redirected to a planeswalker (damage only, not lifeloss), but it doesn't affect the player anymore when you do that.
So cards like Hypnotic Specter won't cause the opponent to discard a card if damage is redirected, since the damage ...