Hanes ComfortSoft: I'll never buy another brand of boys' underwear
I never thought I'd get evangelical about underpants, but here it is. Regular boys' briefs generally come with scratchy elastic waistbands -- they always gave my son uncomfortable red welts on his waist no matter what size he wore. No more: Hanes ComfortSoft boys' briefs are made of the softest cotton, but, more importantly, they enclose the elastic in the same material as the brief. I bought him nine pairs two years ago and they're as study as ever, and only get softer with each washing.
Note: These briefs are on sale at Amazon right now at almost half off: $5.90 for a three-pack (usually $10).