Picking favourites is rather pointless: tea is available in profound variety for the reason that there is a profound variety of ways and situations in which to drink tea.
But, currently in my cupboard:
Loose-leaf:
Gunpowder tea - robust green tea, goes well with conservative amounts of sugar. Good any time of day.
Earl Grey - delicate, and thus reserved for afternoon and on. Best with minimal amounts of sugar and milk.
English Breakfast - I need to find more of these rich Assam-based blends (got some bags from England but they're long-gone). Excellent start-up tea, flexible in terms of adding milk and sugar.
Hunan red oolong - a slightly oolong that's best on the second and third infusions. Great floral tones that call for just a hint of sweetness to make for an impressive (and sort of expensive) of non-black tea.
Bags:
Chai masala - makes for a very flavourful, rich cup that isn't strictly 'tea'. Brown sugar actually complements the spices quite well (wouldn't dare using it in any other teas, though).
Mint green tea - though traditionally served Moroccan with a lot of sugar, I avoid making it that way: excessive sweetness pretty much ruins the light, refreshing nature of this stuff.
Oolong - the smokiness of the particular tea I got, in concert with robustness bordering on black teas, makes this one a bit reminiscent of coffee. Good for an evening tea.
White tea - practically eclipsed since I acquired Hunan red and gunpowder, but I suspect that's because this is bagged crap. Light grassiness with floral notes, but really just bland (not that I expect much from sweepings).