I regard the 2-10-0s as a bit homely...but nothing to puke over.
That's exactly it... they have some nice features, but the proportions ruin it.
My weaknesses in the field of steam are Elescos, Vanderbilts, all-weather cabs, skyline casings and Scullins.
As for diesels (this should get some responses from a different set)...
Again, too many preferences to list. My old standby is the SD80/9043MAC, which I believe to be a popular engine. Among modern power, it's definitely the best. I don't like the more angular nose on the SD90MAC-H II. Interestingly, both GE's and EMD's current products produce the same reaction: nice body, butterface.
Speaking of widenoses, I prefer them without a window in the nose door.
Like most people, I also like the GP60M and standard-nose B40-8, among "modern" power. A surprise was finding I liked the standard-nose C40-9.
Going into second-generation power, I find I like the 20-645 EMDs: SD45 but more so the others: F45, FP45, SDP45 (I like the SD80MAC, how can I not like this?), SD45-2. And I suppose the more esoteric "flares": DDA40X, GP40P-2, GP40X, SD45X...
Just as much as those, the big Alcos: C630, C636, M630, M636, M640. Also C430.
Among switchers, the Flexicoil-truck SW1200/1500.
First generation: Yes, there are locomotives better-looking than Alco PAs. FM C-Liners and Erie-Builts. Even among Alcos, I find the FAs more proportionate... favorite is the FPA-4.
FP7/9s look too long, preferred Fs are the first two phases of the F3 as well as the FT. Among Es, however, I prefer the E8/9 over the earlier models except the E2. I guess I have a weakness for portholes.
Best-looking first-gen hoods are Alcos: RS-2/3, RS-11, RSD-7/15. But also the SD7/9.
First-gen EMDs look bad with chopnoses... but worse with original (sloped) low noses.
Favorite first-gen switcher: S-2 (specifically prefer it over the smaller-radiator S-1 and S-3, and prefer Blunt trucks). Or maybe Alco HH-series.
The DL-109 is NOT ugly.