One option I find intriguing is a chain-pact warlock with Voice of the Chain Master and an Imp or Sprite familiar. For almost every purpose except combat and carrying heavy objects, you get an invisible, flying projection of yourself with unlimited range and no risk. You can teleport your familiar back to yourself at any time (dismiss and recall it), and if it dies you can just re-summon it given an hour and 10 gp.
It will depend a lot on the campaign, but that seems like a very strong ability even into high levels. It's somewhat like Arcane Eye, except it has other senses (and better vision), can move faster and open doors, and you can speak through it and pick up (or drop off) objects. It also lasts longer and can operate without your attention (e.g. "Fly south over the forest for a day and contact me when you spot a tower.").
If the invisible part isn't as important to you, Pseudodragons are also quite nice for their passive Perception of 18 (if the check relies on sight, hearing, or smell).
It will depend a lot on the campaign, but that seems like a very strong ability even into high levels. It's somewhat like Arcane Eye, except it has other senses (and better vision), can move faster and open doors, and you can speak through it and pick up (or drop off) objects. It also lasts longer and can operate without your attention (e.g. "Fly south over the forest for a day and contact me when you spot a tower.").
If the invisible part isn't as important to you, Pseudodragons are also quite nice for their passive Perception of 18 (if the check relies on sight, hearing, or smell).