Geminio

For the wizard that doesn’t have enough: here’s a way to have two of everything you own. Potentially useful for couples’ anniversary gifts.

‘Hermione, we’re surrounded by Dementors!’
‘I know that, Harry, but if she wakes up and the locket’s gone – I need to duplicate it … Geminio! There … that should fool her …’
Harry Potter and the Deathly Hallows

Langlock

Excellent for reducing awkward small-talk at dinner parties is ‘Langlock’ – one of the unorthodox spells Harry learns from the Half-Blood Prince. With this nifty hex, the spell glues the speaker’s tongue to the roof of their mouth, thus protecting the listener from the ludicrous statements they were no doubt making. What a surprise Severus Snape invented this.

Harry aimed his wand at Peeves and said, ‘Langlock!’ Peeves clutched at his throat, gulped, then swooped from the room making obscene gestures but unable to speak, owing to the fact that his tongue had just glued itself to the roof of his mouth.
Harry Potter and the Half-Blood Prince

Orchideous

Don’t be put off by the word ‘hideous’ in the name – this is in fact a lovely spell that causes flowers to burst out of the tip of your wand. Very handy for amateur Muggle magicians, and last-minute Valentine’s Day gifters.

Mr Ollivander ran his fingers along the wand, apparently checking for scratches or bumps; then he muttered, ‘Orchideous!’ and a bunch of flowers burst from the wand tip.
Harry Potter and the Goblet of Fire

The Refilling Charm

This charm, as you may expect, magically refills the glass of the drinker, with any beverage of their choice. Perhaps it’s for the best that we don’t know the official incantation for this one…

Harry had not yet managed to bring off the Refilling Charm without saying the incantation aloud, but the idea that he might not be able to do it tonight was laughable: indeed, Harry grinned to himself as, unnoticed by either Hagrid or Slughorn (now swapping tales of the illegal trade in dragon eggs), he pointed his wand under the table at the emptying bottles and they immediately began to refill.
Harry Potter and the Half-Blood Prince

Glisseo

Stairs are boring, aren’t they? It’s just one step after another. Never mind, because ‘Glisseo’ is the spell that transforms staircases into slides. It can be used in serious events, such as evading Death Eaters, or simply to give your home a bit of an edge at your next house party.

Two masked Death Eaters stood there, but even before their wands were fully raised, Hermione shouted, ‘Glisseo!’
The stairs beneath their feet flattened into a chute and she, Harry and Ron hurtled down it, unable to control their speed but so fast that the Death Eaters’ Stunning Spells flew far over their heads.
Harry Potter and the Deathly Hallows

Tarantallegra

A spell that will come very much in handy if you suddenly realise you haven’t practised for your annual tap dancing competition. Simply cast ‘Tarantallegra’, and the user will automatically become a virtuoso Lord of the Dance.

Gasping for breath, Malfoy pointed his wand at Harry’s knees, choked, ‘Tarantallegra!’ and next second Harry’s legs had begun to jerk around out of his control in a kind of quickstep.
Harry Potter and the Chamber of Secrets