+1 for nzbgeek and may I suggest bundling it with nzb.su. If nzbgeek doesn’t have something you want, nzb.su probably will, and vice versa. I have not found another indexer to have something I could not get with those two. And I have not found a single indexer to have everything. So they compliment each other very well. Plus, they’re not too bad price wise compared to some other well known ones. And registration is public, so you don’t have to wait for an invite or for them to open registration.
You could use just one, and I’d suggest it be nzbgeek, but you will probably be missing some things that the other will have.