I've looked around and haven't seen anyone post this little gem. So, I figured I'd go ahead. Since the price of potions you make for selling is affected by how many effects a potion has, my favorite potion to make is a restore health / lingering magicka damage potion. I use it for selling, which is nice if you don't want to use any cheats for making money. Also, it brings up your alchemy skill pretty nicely. Also, in its favor is the benefit that all these ingredients can be grown in your garden and are readily available from the get-go. It will not work, though, if you have the purity perk.

-Blue Mountain Flower

-Wheat

-Nightshade

My other favorite potion is an invisibility / regen health potion. I believe I've read this one before somewhere but I'm gonna post it anyway. It makes a nice expensive potion, but the second ingredient is a little rare.

-Luna Moth Wing

-Vampire Dust

The most amazing potion I've seen is fly amanita/dragon tongue/mora tapinella which gives 4 positive effects. It's especially strong because all the ingredients are relatively common if you're in the right region.