I’ve recently jumped into a game of Dragonlance despite the fact that all I know of D&D stems from Solasta & the old Neverwinter Nights games. I came to play an Elf Fighter that I want to subclass to Echo Knight. The GM was so friendly to let me rethink my choice of cantrip, which I humbly seek to be advised on. My current favourite is Booming Blade, which I find mixes well with the ability to move out of the current melee by switching with the echo. It also scales in damage the same way I’d receive extra attacks, so I won’t be missing out on much damage in my view. What would you choose, and why?
A fighter using Booming Blade means not benefiting from its Extra Attacks. It’s nice at low level, but replacing 1 or 2 of your swings with some damage if you hit is situational. See this analysis. There are utility cantrips. For use in combat I’d pick a ranged damage spell and Mind Sliver is only Verbal so no need to free a hand up.