Exacting magic omnitool
This looks like a keyfob, with a lever switch, a thin round dial, and a button.
Depending on how you have turned the dial, when you press the button, one of literally every tool that can exist (including attached omnitools) appears fused to the far end of the device, until you press the button again.
The lever switch is a convenience option to lock the selector dial.
The only problem with this incredible object is that the selector dial is unmarked, and due to being able to select from an infinite number of tools, it is VERY HARD (impossible, actually) to effectively use the selector. Even the slightest vibration induced by sound, exposure to light, or air current will push the selector between nearby settings rapidly in a random sequence. Some enterprising owners (perhaps two people in the whole universe) have exploited this device by owning two of them, carefully blowing in the dial to select the "selection cheater tool" (a very precise tool generated by the second omnitool with more usable controls that somehow is able to reliably use the selector knob on the slaved main tool) and glueing the lock switch in position before attaching it to the slave, but the rarity of this item means finding two of them is basically impossible.
The tools manifested by the omnitool are equal in every way to their normal tool counterparts. Toggling the activation button deploys and banishes conjured tools. If a conjured tool is damaged, redeploying the tool will present a functional tool every time. Tools that can be deployed cover everything from the utilitarian, to special use, to "whimsical", and includes such things as blow torches, ropes, vacuum cleaners, keys, magical items, etc. Pieces of tool broken off of a conjured tool vanish from existence instantly.
It is sometimes called a switchblade omnitool, but that is a misnomer.