Yaoi, would be great. be sure to write the manga tiitle.

http://www.mangago.me/read-manga/endou_kun_no_kansetsu_nikki/

Blue sky complex
Jackass!
Honto Yajuu
Home tutor

Basically anything made by Hayakawa Nojiko and Yamamoto Koketsuko

Is this friend okay with the idea or yaoi/shounen ai or would that kill the friendship? One of my biggest regrets in life that I won't ever be able to share my love of yaoi with my best friend. ╥﹏╥

My daughter knows I read yaoi (she's 15) and I recommended http://www.mangago.me/read-manga/love_me_baby_sasamura_gou/ . It's shounen ai and told her it was up to her if she wanted to read other kinds of stories. So if recommending BL I'd go with shounen ai first. If other kinds like shoujo I'd recommend http://www.mangago.me/read-manga/dengeki_daisy/. I guess it's up to how well you know your friend... ╮(￣▽￣)╭

Do you know for sure that this person really likes yaoi? (Otherwise, I would start them off with shounen ai.)

Saaaaaaame!

Of course, it could be amusing to have your very own terror-stricken schoolmate darting side-eyes and haring away at the sound of your approaching footsteps for something so trite.

Bwahahahahaha!l (≧∀≦). Would kinda be fun!