A potion is really nothing more than a spell-on-the-fly; therefore any spell effect can be placed inside of a potion. Due to the potion being limited by Lore (and strength bonuses, from either specialization or focus items), and capped at twice your lore (as recommended in the creating items section), you'll usually only see up to strength 10 potions (until the cap for skills is raised to +6 for the campaign, and then you'll see potions of strength 12). However, it's sort of assumed that you could then add aspects to it above this level?
Thus, potions can work as either evocation or thaumaturgy, and the rules for those sections must be read to determine what a potion can do.
Because you're asking about higher-end examples, I'll use a wizard with lore 5, crafting specialization (strength) +1, and a focus item (magical distillation set: crafting strength +4). So his default crafted item strength is 10.
Evocation effects:
Attack: Flame Tube
Weapon 10 fire attack on one target, targeted with discipline and resisted by athletics. This is the same thing as an evocation fire attack; the user uncorks the test tube and uses his own will to target the enemy with the spell. Could be done with any element.
Variation: Fire Pot
Weapon 8 fire attack on everyone within a zone, targeted with weapons, resisted by athletics. This is an area fire attack, but instead of spending the 1 point of strength on range (lest the caster be set on fire as well), he relies on his baseball tossing skills to physically throw it into another zone. Note that a potioneer with lots of potion slots could technically hand these out to his buddies, and all toss them simultaneously, giving the group four to six simultaneous fire attacks. They resolve separately, but can do in a pack of ghouls quite nicely.
Block Vs movement: Bottled Quicksand
Strength 6 block vs movement for everyone in a zone, targeted with weapons, resisted by might. Lasts 3 rounds. The ground becomes quicksand for 18-24 inches, miring everyone down. Again, the caster relies on his throwing skills to avoid the area of effect. (Alternatively, he makes it strength 5, spends 1 strength on range, and targets with discipline).
Maneuver: Any maneuver can be done to create aspects to tag, but the cheesiest one here is:
Good Luck potion
Strength 8. 3 points to create a maneuver, 1 point to make it sticky, done twice for the same effect. Target receives two free +2 tags to use on whatever he considers "lucky". These can then be used with fate points afterwards for the rest of the scene. This is so.. cheesy.. that I slapped a mild mental consequence of "overconfident" on its use. I did so because I felt like it totally ruined the need to use other skills to make appropriate declarations or maneuvers.
Thaumaturgy:
Zombie Powder:
Strength 10. When poured on a fresh, mostly together corpse, this summons a spirit of hunger into the body instantly, raising it as a standard zombie. You'd best have the drumbeat already playing, as they wake up on the wrong side of the bed quite speedily.
Veil Rip
Strength 10. This "potion" is a piece of paper with a drawing of a doorway on each side. The door is black on a white background on one side, white on a black background on the other. The caster rips the paper in half, creating an opening to the nevernever (or to our world from the nevernever), leading to whatever part corresponds to the location. The tear is approximately 15 feet tall, and several feet across - looking like a rather large doorway. Without interference, the tear closes one round later. This is typically used as an escape potion, but it has been known to be thrown in front of charging monsters.
And so on. Pretty much any effect you can make with a spell, you can make into a potion, as long as you stick to the strength limitations.
That said, I'm pretty harsh about slapping on consequences, as the rules advise when discussing effects that give extra speed and what-not. If you make a potion that gives you athletics 5 for the scene, fine. But if you make a potion that gives you athletics 10 for the scene, it usually costs you a moderate consequence in my game. Otherwise, the dedicated potioneer is better at everything than everyone else in the group. "Oh you have a gunslinger character? well now I have guns 10". And so on.
