One of things that immediately came up when doing character generation with kids for the new Castle Ravenloft/Microlite74 mini-campaign was their desire to play as Tieflings and Dragonborn. It's my fault for introducing them to D&D via Fourth Edition, but that's okay.
I haven't tackled Dragonborn yet, but I think I got the Tiefling right. I went to the D&D 4E and Pathfinder rules for inspiration, and settled upon the following adaptation for Microlite74 Extended Edition.
Tieflings get +1 to Dexterity and +1 to Charisma. Experience Base modifier of +5. Tieflings can see in darkness half as well as in light. Tiefligs may spend 1 HP to add 1d4 fire damage to any attack. This must be declared and spent before the attack roll is made.