Hmmm, you'd probably be safe getting some
London Ale
Irish Ale
European Ale
California Ale
Although many of those can be catered for by the dried yeasts. We've been using loads of US-05 for the past few brews, but coming into winter we're going for porters and dark ales. Maybe the S-04 will do the job, but we've had good experiences with the Wyeast London Ale and Irish Ale packs, so I'd be willing to try the White Labs ones.
The only other time we'd buy liquid yeasts at this stage is for more special beers, like strong Belgian ales, maybe Kolsch (we have a Wyeast pack we're waiting to try), so maybe those more "specialist" ones would be good to have in stock?
Sorry, that was a bit of a ramble... I'm drinking my first ever Guinness Foreign Extra Stout, and it's distracting (in a fulsome way <!-- s;) --><img src="{SMILIES_PATH}/icon_wink.gif" alt="

" title="Wink" /><!-- s;) -->).
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Actually, I think I'd like some European Ale yeast, unless someone can suggest a good dry alternative for making Alt.