I'll list them all here including ones we've already completed or may not need to address, just to make sure none slip through the cracks. Per https://jquery.com/upgrade-guide/3.0/ we have these:

Deprecated

• jQuery.fx.interval (PR Deprecate jQuery.fx.interval as of 3.0 #969)
• .toggleClass() and .toggleClass(Boolean)
• jQuery.unique renamed to jQuery.uniqueSort
• jQuery.parseJSON
• .ready() signatures other than jQuery( fn )
• easing parameters (issue Document jQuery.easing for adding easing functions #766)
• .bind() and .delegate() (PR delegate: Document the method was deprecated in jQuery 3 #948)
• jQuery.expr[":"] and jQuery.expr.filters (issue Add Sizzle wiki as API page #1224)

Removed

• jQuery().context and .selector (needs change to text, see Selector: Move from global to instance property category #1030)
• .andSelf()
• jqXHR.success, .error, and .complete (there's proper text at https://api.jquery.com/jQuery.ajax/#jqXHR)
• $(document).on("ready", fn) (never documented?)
• .load(), .unload(), and .error() (tweaked in All: Mark event aliases as deprecated #1223 to separate event descriptions from shorthand pages)
• event.pageX and event.pageY normalization (not sure we need changes)

Features

• jQuery.escapeSelector
• jQuery.ready promise-consumable (issue $.ready documentation #205, PR Document jQuery.ready #983 (was: Document jQuery.ready as Promise-consumable #530))
• jQuery.Deferred Promises/A+ compat
• jQuery.when() consumes thenables (issue Document jQuery.when changes in 3.0 #921)
• .animate() uses requestAnimationFrame
• settings argument signature for jQuery.get() and .post() (showing 1.12?)
• SVG support for .addClass(), .removeClass(), and .toggleClass() (showing 1.12?)