The Adrenaline milestone weapon from Virus can be glitched to make the speed boost semi-permanent. (This also has the side effect of removing the distortion effects drawn on the edges of the screen.) Simply equip the Adrenaline, use it, then remove it from your hotbar. The speed boost will last until Adrenaline is re-equipped or some other outside force modifies the player’s speed/state, such as a minigame (I’ve only tested the latter with Target Practice).
I recorded a short clip of gameplay demonstrating the glitch, as seen below:
However, this bug report comes with a rather significant caveat. I view this bug as rather harmless, as it does not seem to have any potential for abuse. (The only thing I could think of is the speed boost carrying over to Laser Tag, but I haven’t tested that.) As such, I would like to make a request: Unless this bug is found to enable some form of abuse, please, either do not fix it, or find some way to implement it officially.