There is a small cabin between helgen and riverwood and I found a daedric crossbow laying on the floor at level 5... no clue what mod put that there.

Running crossbows expanded?

drop it to the ground.

open the console and click on it.

the first two digits will be the mod index.

Look for the index in bash.

DaedricCrossbow.esp

It requires Dawnguard.

That's one I used for a long time before I stopped using it because the animations were a bit weird with it sometimes. That and I was slashing throats with it o_o.