I have some baby ideas (I haven't 100% the game yet, so if some of these are already in, then I apologize in advance)...
Lil' Monstro: Very slow attack speed with short-range; however, it shoots in its lane and two adjacent ones.
Robo-Baby: Fast speed, low damage; damages all enemies in its row.
Seraphim: Great damage and homing; it becomes invulnerable when enemies get close to it; however, it also stops attacking in this state.
Lil' Gurdy: Works like bowling walnuts.
Fat Protector: Slightly less health than Cube of Meat; however, it is able to stop the red fly enemies (I don't know its name).
Sister Maggy: Works like B. Bobby; however, it is slower, does less damage, but it gives small hearts every few minutes.
Rotten Baby: Shoots charmed flies :>
Little Gish: Low damage and shot speed; however, it slows enemies down for a longer period of time.
I also have some item ideas, but I'll stop here for today.