I think open-breach weapons are what the OP may be looking for.
Most (all?) semi-automatic weapons are closed-breach - to load, you cock the mechanism back and forth in the same motion, with the forward motion grabbing a round from the magazene and sealing it into the barrel. Pulling the trigger releases a hammer (which was loaded back during the backward motion of the mechanism) which hits a pin and fires the bullet. The recoil/gasses then pushes the mechanism back for anothe bullet.
Open-breach weapons, OTOH, chamber the round and fire it with the same motion; the default condition of the mechanism is pulled to the back, and pulling the trigger simply releases the mechanist forward There is no independant spring-loaded hammer. Theoretically, with an open-breach weapon one can put the magazine in and simply pull the trigger to fire, if you had the mechanism pulled back to begin with.
However, most users do not walk around with the slide back - for safety reasons, obviously, and to prevent spring fatigue. Additionally, most open-breach weapons are heavy, belt-fed automatic weapons like machine guns; the only exceptions I can thing of is certain older sub-machineguns like the Uzi*. So theoretically, yes: you can put a magazine in an Uzi, pull the trigger and open fire. But only if you don’t know what you’re doing.
*I’m pretty sure that the more modern Uzi varients, such as the Mini-Uzi, Micro-Uzi and Uzi Pistol are close-breach.