The Living Tribunal (Marvel) is the overseer of the Marvel universe.
Solaris (Sonic the Hedgehog) simultaneously exists in the past, present, and future, making him omnipresent (only throughout time).
The Master Emerald (Sonic the Hedgehog) is a transcendental object that exists simultaneously in all time lines across the time-space continuum. That means should the Master Emerald disappear in one time frame, it would cause a chain reaction that would make the Master Emerald disappear in all existing time frames.
The Time Eater (Sonic the Hedgehog) is an almighty entity of time.
The Elder God (Legacy of Kain) is "eternally present, here and everywhere, now and always."
Schrodinger's (Hellsing) ability of being everywhere and nowhere extends even to very subjective realms.