I can often tell just by the cover who the seme and uke are going to be. I'd love a manga where the roles might be surprising, or unexpected, or just unconventional. Examples:

• shorter seme, taller uke
• manly uke, girly seme
• submissive seme, dominative uke
• seme mistaken as a girl
  Etc. etc...

There are a lot of mangas like this... You can try searching for categories and see the mangas that you like more (story/art). I'll edit for more later.

http://www.mangaupdates.com/series.html?category=Tall+Uke
http://www.mangaupdates.com/series.html?category=Older+Uke+Younger+Seme
http://www.mangaupdates.com/series.html?category=Crybaby+Seme
http://www.mangaupdates.com/series.html?category=Feminine+Seme
http://www.mangaupdates.com/series.html?category=Naive+Seme%2Fs
http://www.mangaupdates.com/series.html?category=Seme+Turned+Uke (maybe?)
http://www.mangaupdates.com/series.html?category=Seme-like+Uke
http://www.mangaupdates.com/series.html?category=Uke-like+Seme
http://www.mangaupdates.com/series.html?category=Tough+Uke
http://www.mangaupdates.com/series.html?category=Masculine+Uke
http://www.mangaupdates.com/series.html?category=Dominant+Uke

Kizudarake no Airabuyuu, trust me.

if there is an option between "to do" and "not to do", I will always choose the latter.

"what kind of crazy, twisted conclusion is that...?" - banana bread no puding

Also try these threads
Non-stereotypical yaoi, for ex. Short Seme/Tall Uke
Can anyone suggest a yaoi where the uke looks like a seme?

Akiyama-kun
Akiyama-kun
Akiyama-kunnnn <3

It's the Art of Time, it's the Art of Life--
Of the player and the craftsman,
Of the writer of songs, of the creator of love,
Of those who will follow, of those who led,
There's no other way in the world ahead ♥