Orb of light, Omochao, question mark with rainbow ring.
Hints are helpful advice given to the player during gameplay. The kind of advice given varies depending on the location. They give the player useful information to help you in situations such as an obstacle or a new gameplay feature.
List of Hints Types
First and only appearing in Sonic Adventure, the Hint Orbs were floating red and white sphere of light that hover just above the ground. On contact they will circle the character as it gives advice to the situation the hero has to overcome. Sometimes Knuckles will find a Hint Orb which will show him exactly where the piece of the Master Emerald is located.
The Hint Orb is also Tikal's spiritual form. Evidence is that the voice of the Hint Orb is her own and when Perfect Chaos threatened to destroy the world again, she appeared to Sonic as a Hint Orb before her regular appearance.
Floating computer monitors that give you information. Unlike Hint Orbs they stay in place but won't activate by touch, instead they are meant to be talked to (by pressing the Action button when close to one).
They first appeared in Sonic Adventure, but mostly in the Adventure Fields. Hint boxes are interacted like with any other NPC.
They appear again in Sonic Adventure 2 giving clues to Knuckles or Rouge on where the treasure is hiding usually in a riddle form at a cost of points. They could be given up to three hints. In 2-player Emerald Hunt games the use of Hint Boxes is limited and only time-by-time.
While not an official appearance, Hint Box could of been inspired from "Cheat cards" seen in Sonic World from the game Sonic Jam. Also 3 large yellow versions of the Hint Box appear in Sonic the Hedgehog (2006) (1 in each town stage), but they are more for shopping than anything else.
Omochao is a robotic chao with a propeller on its head. Its name is a portmanteau of the Japanese word omocha, meaning "toy", and Chao. He replaces the Hint Orbs in Sonic Adventure 2 dispensing a variety of advice. Omochao also had other uses such as a being used as a throwing weapon to sometimes humorous results. Omochao can also be attacked (whether it's accidentally misfiring or purposely) and will say quotes like "That hurt!" or "I'm not gonna help you any more!".
Hint Rings appeared for the first time in Sonic Heroes. On contact, the playing character or companion (or sometimes even a narrator) will tell advice for the situation. The Hint Ring originally was a question mark centered in a rainbow colored sphere. But later series became a golden question mark with colorful orbs circling it vertically. However, the more hints the player asks for, the lower their score is.
Also in Shadow the Hedgehog the hints markers in Expert Mode are found once at the beginning of every level and only offer good luck. No other hint markers are offered in Expert Mode. In Sonic the Hedgehog (2006), Hint Rings appear, looking exactly as the ones from Sonic Heroes. Hint Rings also appear in Sonic Unleashed. When activated, Chip will give advice concerning where the player is. They also appear in Sonic Colors, with Tails giving the hint. They are found mostly in Tropical Resort, and explain to the player how to use Wisps. In the DS version, Tails explains to the player how to use Wisps. It should be noted that Hint Rings did not appear in Sonic Generations due to Omochao serving as their replacement, but they reappear in the Nintendo 3DS version of Sonic Lost World. In the game, many hint rings are seen in the tutorial act of Windy Hill.