1. Powerhouse. Pec Night. Drink specials for guys who don't wear shirts. When: 10 p.m. Where: 1347 Folsom St., between 9th and 10th. 2. Endup. Fag Fridays. Contemporary house music for young and hip partygoers. Resident DJs: Rolo, David Harness, Pete Avila and Neon Leon. When: 10 p.m. to 6 a.m. Where: 401 6th St., at Harrison. 3. The Cafe. Boy Bar. Promises high testosterone, low attitude and tight jock straps. When: 9 p.m. to 2 a.m. $3 cover. Where: 2369 Market St.