Gideon, Champion of Justice

Gideon, Champion of Justice's power and toughness are set to the number of loyalty counters on him when his second ability resolves. They won't change later in the turn if the number of loyalty counters on him changes.

Say you activate Gideon, Champion of Justice's second ability, and then an opponent gains control of him before combat. You may have any of your creatures attack Gideon, Champion of Justice (since he's still a planeswalker). Then Gideon, Champion of Justice may block (since he's a creature). He may block any eligible attacking creature, including one that's attacking him! During combat, he behaves as an attacked planeswalker and/or a blocking creature, as appropriate. For example, he deals combat damage to any creatures he's blocking, but he doesn't deal combat damage to any unblocked creatures that are attacking him.

Gideon, Champion of Justice's second ability causes him to become a creature with the creature types Human and Soldier. He remains a planeswalker with the planeswalker type Gideon. (He also retains any other card types or subtypes he may have had.) Each subtype is correlated to the proper card type: Gideon is just a planeswalker type (not a creature type), and Human and Soldier are just creature types (not planeswalker types).