While I'm sure people probably get tired of me bringing up his name, Harry Dresden has a few companions who could arguably be thought of as "familiars."
There's "Bob" - a spirit of intellect trapped in a human skull who can only go out in daylight if he possesses some creature (and Harry lets him do it). Harry often has to negotiate "weekend passes" for Bob to get him to do some work. Bob does recon for Harry and he's an invaluable resource for prepping spells and potions.
Then there's Harry's cat "Mister" who's a giant (30+ lb.) grey tomcat. Mister's pretty bright, but he's just a cat, although Bob frequently possesses him.
Finally there's "Mouse," Harry's ridiculously smart, half-celestial "Wooly Chowmoth." Mouse is a guardian (Foo) dog, and is more like a druid's animal companion than a familiar.
I like the idea of familiars as resources (scouts and guides), rather than as combatants. I think there should be an incentive for casters to keep their familiars alive so they don't risk them unnecessarily, but I agree that familiars make far more sense as an "option" rather than as a requirement.
Birds of all sorts, bats and cats are pretty traditional familiars, along with rats, toads, weasels and miniature dragons. Similarly, the Tressym (winged cats from FR) make a pretty "cool" addition.