In D&D 5e, Half-Dragon is a template (MM, 180) that can be applied to any beast, humanoid, or giant. When I applied the Red Dragon Wyrmling's dragon breath - which deals 7d6 fire damage in a cone - to a Raven (CR 0) it came out as CR 1/4 (according to the creating a monster section of the DMG).
Druids can Wild-shape into any creature CR 1/4 or lower, starting at 2nd level (or Circle of the Moon Druids can Wild-shape into CR 1 creatures).
This would mean a level 2 Druid can wild shape into a creature that can deal 7d6 fire damage in a cone, with a 1/3 chance of being able to reuse it every turn. This is more damage than any other class can deal at this level, even with max stats (eg. a fighter action surging [once per day] deals only a max of 4d6+10, approximately the same as this, which the druid can do infinite times in a day). So, can druids Wild Shape into beasts with the half-dragon template?