Shot an M4 while in Afghanistan and for those who don't know it has a collapsible stock which is the way I carried it normally and it is designed for right handed shooters. I'm a lefty, so when the necessity came to fire that thing "On short notice", that hot brass felt like it was tickling the end of my nose, but in reality was about 4 inches away. I can honestly say, I wouldn't be real keen on spending money on a gun where my face is about an inch from the ejection port during operation. Can't see a bullpup or any of those "shorties" in my future, but they look cool.
The bullpup in the above picture is an IWI X95 Tavor. Safety and magazine release are ambidextrous and the charging handle and bolt/ejector can be swapped for left handed parts so it ejects on the opposite side.
The Kel-Tec RDB ejects out the bottom so the brass burns your nards when you’re driving around in your underwear shooting at coons and possums from the drivers seat. Or so I’m told.
As Supressyourself mentioned, the Desert Tech MDR can be right or left ejection and you can swap calibers on a single chassis. I believe you can run .308, 6.5Cr, and .223 all in the same gun (with some parts changes).