"Why not ask Professor Snape to show you how to whip up a Love Potion! And while you’re at it, Professor Flitwick knows more about Entrancing Enchantments than any wizard I’ve ever met, the sly old dog!”
-- Gilderoy Lockhart on Valentine's Day (CS13)
Spells that cause the target person to fall in love with the caster.
References from the canon
Lockhart suggested that Flitwick was an expert in these, much to Flitwick's embarassment (CS13).