Depends on what style you prefer. Last weekend I shot a wedding at Baur au Lac - very posh, but quite formal, like all these Grand Hotel weddings. The weekend before I was at Jucker Farmart, wedding in an old barn, party overlooking Pfäffikersee, very relaxed, very Swiss (in the positive sense). http://www.juckerfarmart.ch/priv_events.phtml
Thanks Frank! Nothing too posh and nothing too casual. Really looking for somewhere we can eat and party until dawn (if that's allowed!!). I take it you're a photographer? Are you for hire??!!
I've seen quite a few summer weddings taking place in Hotel Sonne near my house. The guests had exclusive access to their garden right on the lake. Hotel is easily accessible for guests from the Küsnacht HB (3 minutes walk). Very pretty and the restaurant's food is pretty good too.
Both were excellent for their food - the latter was a nice place to get people together without being too "poncey".
Greulich were unbelievably good - tailored the menu, left in charge of the cake - and ordered/sorted the table decoration - in fact we did pretty much naff all to organise both parties.
Unfortunately I can't recommend a venue but Fräulein Meier at www.ohsweetestthing.com can make you a lovely wedding cucpake tree; a nice alternative to the traditional wedding cake.