My favorite is English breakfast in any of the common brands (Tetley, Scottish Blend, Twinings etc).
But my second favorite is Chai. Twining's Chai is nice, but I have a real thing going on for Chai lattes and I've recently found my local supermarket stocking Chai latte mixes (I think the main difference from normal Chai is the sugar). This place
does a nice Vanilla mix, but I love cinnamon so I'll need to pick up their Spiced Chai for a bit of stronger flavour.
I recently found Celestial Seasoning's "Sleepytime"
tea in the shops as well - keep meaning to try that one out, but I'm a milk-in-my-tea junkie and I'm not big on herbal mixes so it might take me a while to get around to it.