I recommend on general runs (aka these don't need synergies) Deserter, Fiend Friend, Frozen Baby, Imp, & Tooth & Nail
Most of the unlocked babies power creep their competition so I use them. Unlocked ones I like are Tooth & Nail, Paschal Candle, Psychic Baby, Fiend Baby, Deserter (Ofc, it's op af I know, I'll explain why if needed), Dry Baby & Parasitoid.
In terms of babies which come without being unlocked include B, Bobby, Cube of Meat, Bob's Brain, Frozen baby. Mongo Baby, Multidemensional Baby, Spider Baby, Spike Baby, Imp (from Mystery Gift item) & Little Steven .
What I use depends on what else I'm using, like I use Paschal Candle with Brother B. (if I don't have any other lane shooter) or with Psychic Baby.
Some things like tank (referred to as defensive babies in the game) babies are amazing with Frosty Mint and/or Sanguine Bond.
