here's the ones i recall that have sued over royalties recently...
UTA: $43,000 unpaid for Blade Trinity Soundtrack (10% of his advance)
U-God: $170,000 unpaid for signing to Wu Music Group
Ghostface: $158,000 unpaid for dispute to owning 50% as producer
Bridgeport Music/Westbound Records: Copyright infringement, unfair competition, and lawyer fees for uncleared sample of "New Wu" (illegally used a sped-up four measure portion of the “I’ve Changed Track”)