Joby Ballhead X
I went through a phase (and several ball heads) trying to find a good strong and trusty ball head that didn't cost an arm and leg and ended up "accidentally" coming across the Joby Ball Head.
AND it costs less that 50 bucks!
I 99.9% trust this ball head to hold my most expensive gear and have been using these ball heads for almost 5 years now without 1 of them failing yet! (and I don't baby them).
I use all arca-swiss types of clamps and mounting plates and have modified these Joby Ball heads and fitted them with those styles of hardware.