I have to say after changing my diet to a much healthier one, I haven't really had the need. I haven't had a cold or the flu for 5 years? It's been so long I can't remember anymore!
But here's some of my favorites, tried and true:
*Plantain - wonderful as an anti-inflammatory - I used it on my knees for a few years, they used to hurt like crazy all winter long, but now they don't bother me anymore. But it's also excellent on insect bites and stings.
*Geranium essential oil - EXCELLENT for bruising, but you need to get it on within a couple minutes of the accident or it doesn't work as well. I'm pretty accident prone, I run into all sorts of things - mainly corners of tables

but occasionally the dogs jump on me or get me with their claws. Or Carl will back into me with his tail-stump - i know that sounds funny, but that HURTS!!! I put it on "neat" (no dilution) directly onto the affected area, although I've never used it nor do I recommend it undiluted for broken skin, and wow, it gives such a warm, caressing feeling, and I don't get a bruise at all.
*Tea Tree is a wonderful anti-microbial, antibacterial, antifungal oil. Use it on warts, scratches, skin irritations, abrasions, and blemishes. You can use it undiluted, but it can dry out your skin.
There's lots more but these are the ones I use most.
Oh, and calendula is wonderful for diaper rash . . . but first I have to have a baby to be able to use it for that!