One of the Puppet Master movies? They're pretty campy, but some have some weird sex scenes in them (Though they're usually pretty brief). I don't think parts 4 or 5 do though. I would say 2 or 5 would be especially good as "b-movie hooks", 2 is the most "out there" (Aside from the non-effort Vs. Demonic Toys), and 5 has the puppets as good guys fighting a little monster thingy with the help of the sagely spirit of their old master and a slightly dorky "boy-toy" new master, plus plenty of fake-looking blood. It continues directly from part 4 but there's a recap at the beginning. If you can find the videocassettes (Which is the hardest part) I'd set up a double-feature with parts 4 and 5.
From what I've seen Uninvited looks like prime material to start out on b-movies, but I haven't seen the whole thing so I can't be sure. PG-13 but still plenty of blood and some sexy moments is what this clip suggests:
. Andrew has a review on the main site so you may want to check that out.
Godzilla flicks are also good as a starting point, unlike some things I've listed a good majority are readily available on DVD. A warning though, while most contain awesome monster fights some can be pretty serious. Godzilla Vs. Monster X is probably a good place to start, three monsters and weird aliens to boot!
Considering stronger female characters, I think of Cursed. I only saw the TV edit so I don't know how much "bad stuff" is in it but the girl is neither a damsel in distress or a cliche tough chick. In Scarecrows (1988) there's no real romance at all despite the two prominent female characters, the good one is pretty tough.
The House series (1986-1992) are plenty campy and have a good bit of monster mayhem. The first two even have a bit of emotion and
intentional humor to balance it out. I haven't seen the third but I wouldn't exactly recommend the fourth, it's
really bad and has a close-up on a chick's bloody boobs. Also if you're looking for gore, monsters, and weird characters check out Waxwork, or for just monsters and odd characters see if you can find a copy of Spookies anywhere.
Hopefully at least two of these will have enough action to keep your friends awake and interested, and have enough weird stuff to make "B" mean "good" for your pals.