I love wine tasting. I don't discriminate by varietal, in fact, I will try just about any kind of wine, no matter the reputation (sorry, not all Merlot is bad), and then decide on a case by case basis (pun not intended). So if it's up to me, I would love to give guests the option to choose from 5 reds and 5 whites, plus 3 dessert wines.
Off the top of my head, I would choose: Syrah, Cab Sauv, Zinfandel, Merlot and Pinot Noir. And that doesn't even get us into the fun varietals like Malbec, Brunello, Mourvedre, Barbera ... I can go on. For whites I would probably choose: Champagne, Sauvignon Blanc, Chardonnay, Pinot Grigio and Viognier. Gewurztraminer or Roussanne anyone?! And for dessert, probably a nice thick Port and an Ice Wine, and maybe a Moscato.
Pretty unlikely though for a wedding, because depending on the bar, you can't have that many options or you have to pre order bottles and that just gets to be a lot to try to premeditate what your friends will actually end up drinking. So how do we narrow it down?! You have to read your guests and your event. Main things to hone in on:
Time of Year: Is it winter? Clearly you'll need more red. Is it summer and outside? Order more white! I think it's always nice to give a guest 2 choices of red and 2 of white. Then if possible, throw in a third choice for whichever you will likely be serving more of. If you are serving sparkling wine, you should definitely be good with 2 other whites and not need a 3rd.
Big Winos: If you know your guests are a big wine drinking crowd, chances are they like some bigger wines. If they're not, then don't get too adventurous and stick with more simple, mainstream varietals.
Location: Are you in a foreign country or in a wine region? Definitely go with some of the favorites of your location, but don't scare people off with names like Gruner Veltliner and Teroldego. If you do choose the adventurous side, make sure guests can have a taste and serve a more commonly known varietal alongside it so they don't feel overwhelmed.
Bold and Light: Be sure to choose somewhat opposite options for guests. Everyone doesn't necessarily pair their wine perfectly with their food (nor do they care), but make sure if you offer a bigger wine like a Syrah or a Cabernet Sauvignon, that you offer a lighter wine like a Pinot Noir or Merlot. Same goes for whites. While you may think of them all as "light", try and choose an oaky wine vs. a fruity wine or vs. dry. Think Chardonnay vs. Pinot Gris or Sauvignon Blanc.
As much fun as wine tasting can be, you really just want to give your guests a few options so they feel deliciously satisfied and like they get a choice, without giving too many options that will hold up that precious bar line.
And don't forget! Brides should be drinking white wine to prevent any possibly red wine spillage! So not worth it even if you are a red drinker...