I agree fully on Jenssen. The screenshot is him at the end of my second season with Betis. He plays as my dlp-s in a 4-3-3 and has been excellent. On the surface his stats don't look that impressive (1 goal and only a handful of assists), but was tied for first in pass completion (with Xabi Alonso at 90%) and was also in the top 10 in key passes. He had to lead La Liga in pass leading to the assist. All that and I only paid like $2 million. Also, the only time that he ever complains is when I drop match prep to "very low". Kara is right up there as well. Of course, everyone knows about these 2.
Some other players that I love who are well-known, but aren't on every "must-buy" list have been James Rodriguez and Gerard Deulofeu who both cost me around $8 million dollars (previous patch). However, my favorite players to sign are always Isco, Rafinha (from Barca B) and Davide Astori.