I see a lot of good ideas for a pair of small fish (which is what I would do) . . . I think it's tough to think of one fish that would look good in a 29G . . . when I think of firemouths or rainbows or convicts, I usually think of them in pairs or as community fish; hard to picture them as a single show-piece fish . . . (?)
that's what I found so tough; I can' think of too many fish I'd keep solo, except for the bigger cichlids . . . I guess that doesn't really help, tho' . . .