By far the best cosmetic DLC for Stellaris
I'm not normally into cosmetic DLCs, but I've *really* enjoyed Humanoids.
There are a few reasons for this:
1) The DLC's humanoid ship set has easily the best looking ships and starbases in the game.
2) The voices the DLC provides are underrated and were an unexpectedly enjoyable addition to the game. Since Stellaris already has a great soundtrack, I'm less likely to mute the game and more likely to enjoy the DLC's voices.
3) A large number of prescripted empires use the humanoid ship set and voices. This DLC meshes well with those, which spawn as AI empires even if you don't play as them.
Obviously this isn't as beneficial as DLC that affect Stellaris's mechanics, but I have no regrets about having picked it up on sale.