Some of these are more medium arms and this is not a complete listing of the concepts. Some aren't really concepts either but old fashion making a come-back.
The first one is compact Coil Rifle (electo-mag) with a sonic knife slung under the barrel/sighting laser
Believe it or not Shotgun's are still in service. When lasers, mag-coils, and plasma-injectors fail you will want something like this as a back-up.
With HE, AP, Grenade, Frag and even more exotic loads it's more then formidable as a main weapon. Especially with a drum-fed semi-auto attachment.
Tactical Tomahawk and a combat knife are always old standbys.
The big-boy at the bottom is a plasma-rifle What looks like a clip is a heavy duty battery. When operating in vacuum it has it's own Gas pack that is attached below the wielder's air tanks.