My party is introducing a new house rule, signature moves/spells. 

At level 5, characters have honed a certain move or spell so much that it becomes their signature and they can derive more benefits from it. We made it either moves or spells so that both spellcasters and martials can benefit from it (half-casters can choose between either a signature move or spell). Every five levels, we can change our signature move/spell.

A signature spell is basically tweaking an existing spell to make it stronger. A signature move is a freshly homebrewed ability. 

Help me figure out a signature move or spell for my character, a vengeance paladin bladesinger wizard multiclass! I would be happy to receive suggestions for any tier of play. Signature moves/spells also do not necessarily have to be combat related! 

I rolled amazing stats so no worries about that, and I'm playing a Dex-based build. I will start with 2 levels of paladins, then 6 of wizard, the 4 more of paladin, then finish up with wizard. I'm focusing on nova dps. 

An example signature move we thought of for low tier:

Blood Song: Once per short rest, you can make one weapon melee attack immediately after you activate your bladesong.

Can you just take other subclass features as your signature move? I have a homebrew rule that achieves the same effect as this (though the setup is very different).

For my campaign, a monk character earned the Fighter Samurai's Rapid Strikes ability: they could forego advantage on a single attack to make an additional attack, both of which without advantage. We called it his Soul Split ability, and it was tied to his backstory. That was a fun thing, and certainly opens up more avenues for you to consider. 

When you jump from a place ten feet above you and do a weapon attack, any creature who gets hit by it is dealt 1d4+1 slashing damage for every point of damage you sustain from the fall.