Harry Potter spells (M-R)

Melofors (Magic-User 1)
Casting time: 1 segment
Range: 60'
Encases the target's head in a pumpkin. Other objects can also be encased in pumpkins if you feel the need.

Mobiliarbus (Magic-User 1)
Casting time: 4 segments
Range: 40'
Allows the spellcaster to levitate trees, as per the Levitate spell, but only with trees.

Obliviate (Magic-User 5)
Casting time: 1 round/clause
Range: 30'
Erases or modifies the target's memories. Far more powerful than the lower-level Forget spell, Obliviate will allow the spellcaster to make complex adjustments to the target's memories. However, the spell takes longer to cast the more complex the modification, where each clause of the spellcaster's design adds another round. For example "I'll make him forget that we attacked him, and instead remember he was attacked by the goblins," would be two clauses - one erasure and one inception.

Oppugno (Magic-User 3)
Casting time: 1 round
Range: 60'
Duration: 1 round/level
This spells causes small inanimate objects or small mundane animals to attack the target. Only one class of objects can be affected (i.e. "birds" or "newspapers") and the number of objects is equal to 1d8xlevel. Generally speaking the attacks will be irritating and delaying rather than damaging, though the DM may rule otherwise in certain situations (say, with a swarm of knives or venomous spiders).

Ossio Dispersimus (Magic-User 1)
Casting time: 3 segments
Range: 40'
Saving throw: Negates
Causes all the bones to vanish from one limb.

Piertotum Locomotor (Magic-User 3)
Casting time: 1 round
Range: 60'
Duration: 2 rounds/level
Animates up to 2d6 suits of armour, causing them to fight as 1st-level Fighters in service to the caster. The suits have 1d4 hitpoints for leather/light armour, 1d6 hp for chain/medium armour, and 1d8 for plate/heavy armour. If reduced to 0hp they will fall apart rather than be destroyed.

Portus (Cleric 7)
Casting time: 1 turn
Range: 20'
Cost: crushed gems and golden doorknobs worth a total of 1,000gp
This spell turns one inanimate object into a portkey, a device that will instantaneously teleport anyone who touches it. The destination of the teleport is the place where the portkey was created. The portkey is always teleported along with the creature who touched it. Each time the portkey is used, there is a 5% chance that it will malfunction, ruining the portkey.

Prior Incantato (Cleric 1)
Casting time: 1 round
Range: Touch
Reveals the last spell that was cast by a particular wand.

Protean Charm (Magic-User 1)
Casting time: 1 round
Range: Touch
Causes up to 10 inanimate objects to be linked through space so that whatever happens to one of them will happen to all of them.

Other well-known spells:
Nox 'Darkness'
Petrificus Totalus 'Hold Person'
Protego 'Shield'
Reducio 'Shrink'
Reducto 'Disintegrate'