Some time ago, I found some interesting LEGO patents at USPTO, filled by Interlego AG (Switzerland) at the time.
One of them describes a part similar to the actual LEGO TECHNIC Angle Connectors, but like a cross, which would allow to connect four TECHNIC axles and was never released up to date in any LEGO set. As the other Angle Connectors, maybe it could be also of interest for many of us.
The patent was filled in 1996 and published one year later, in 1997. The same year when the first TECHNIC sets using those similar Angle Connectors were released, like the mythic 8479 (Barcode Multi-Set) or 8250/8299 (Search Sub) among others.
This is of 'Design Patent' type and Claims for an 'ornamental design for a building toy element'.
Some other interesting Angle Connector variations, could include Acute rather than the known Obtuse, Right or Straight angle parts. Like the red example parts, proposed in the images below, which were found at Brickshelf and would allow a new set of possibilities.