What scale is 'best'?

[Mr. Peabody]

I went for 15mm.  Reason being, there's more figures for it.  HO scale buildings work really well with 15mm, and I hear for 20mm as well.

Now if you want to narrow down the range of figures, say you just want Weird War II with Nazi Zombies, there are some great 20mm ranges, but for sheer choice 15mm is the way to go.  Ultimately, it's your preference, but talk it out with your gaming group and see who's willing to go in with you.  Sucks being the only one providing the minis.

Maxim is spot on the money, especially with the last bit...

I love 20mm and have dabbled with 15mm too, but my gaming buddies who enthusiastically collaborate with projects are committed to 28's. That collaboration makes all the difference. 

[Maxim]

D'oh, I didn't post that pic.  Here it is!  Ok, I didn't do anything to this building other than the furniture.  I bought it this way for like $15-20, including shipping.

[Mr. Peabody]

There are a couple of classic HO kits from 'Model Power' that are perfect for Post-Apoc.

Chester Urban Renewal Project and Burned Town House

[Damas]

Mr P and Maxim, thanks for the great advice.

As for the gaming group, they are all die-hard 40k players so if something new is proposed, it has to come fully complete.    Also, I have no prior 28mm scenery so I'm not worried about starting from scratch.

[3 fingers]

I suppose it depends on what your doing foot skirmish then you could do 28 mms but if a lot of vehicles are involved then maybe consider 20mm
I have fond teen memories of hot wheel cars being converted for dark future with Matt paints and 40K or 1/35 scale guns with the stocks cut off and glued to the cars,wasn't there  a not dark future line of 20 mms people Stan Johnson?

[Darkoath]

Yes if you are planning to do skirmish level for your zombie games I definitely would go with individual 28 mm miniatures.  You could have hundreds of different models
with no two identical.  Also using 28 mm, there is probably the most available for terrain if you use O scale model railroad stuff in addition to what is available in 28mm in metal and resin scenics.  Getting diecast vehicles is also easier if you are doing 28 mm.  In the smaller scale you also do have HO scale model railroad stuff to work with too however.  My choice
for skirmish level games has always been 28 mm.  I use my fields woods scrub fencing etc from everything from FIW to modern zombies games... all using O scale and 28 mm items.