Sweepstakes

A vertical built on prize giveaways — "win an iPhone," gift cards, cash — where the user just submits an email or fills a short form to enter. The barrier is a single opt-in, so conversions are cheap and volume is huge, which suits push, pop, and social traffic. Payouts per lead (SOI or DOI) are small, so you win on scale and a tight funnel rather than fat commissions.