Here's a list of my personal favorite movies that are by no means good, but are very entertaining:
Schwarzenegger has to have a couple of movies on that list. If I must pick favorites, it's hard to wrong with these ones:
Commando
Predator
Kindergarten Cop
Total Recall
If you're going for a more horror approach, I've heard that Peter Jackson's earlier works are great in that sense. But I've heard the best of them is:
Dead Alive
I'm a big fan of Will Smith, and while his movies aren't necessarily "B-Movies" by everyone's definition, they're entertainingly bad[footnote]Men in Black and Independence Day were left off this list for being too close to actually good movies. Rest assured I have no lack of love for either.[/footnote]. In particular:
Wild Wild West
Bad Boys 1&2
If you want to go with wacky sci-fi and fantasy, there are a few classics and some lesser known ones I can recommend. Here they are:
Time Bandits
Heavy Metal
Highlander
The Road Warrior
Epoch
Mortal Kombat
Immortal
And if you will allow me to combine this with the first category, then:
Red Sonja
Conan the Barbarian (best watched with commentary on)
While not always "B-Movies", old school Jackie Chan movies are super campy, super entertaining and contain a load of awesome stunts and martial arts. I highly recommend:
Police Story
Police Story 2
Police Story 3: Supercop
Jackie Chan's First Strike: Police Story 4
The Drunken Master (not to be confused with The Legend of the Drunken Master)
and even...
Rush Hour
Those are just a couple of my favorites, I may come back when I remember more...