Ben Stiller (Mashup Germany) consistently puts out awesome mashups. Well, at least mashups that sound awesome until about half way through the song. Then, out of nowhere, Stiller will insert a completely incongruous sample.
Example: Matisyahu vs. John Lennon vs. Blink 182 vs. Bob Marley vs. Gentleman - Imagine One Day (so far away)
This song is awesome until about 1:20 when Blink 182 comes in. WTF. Why? If Stiller would just cut out the crappy middle school pop-punk and add more Lennon or Marley, this mashup would be killer.
Example 2: David Guetta feat. Akon vs. Mashup-Germany - Sexy Bitch in Memphis
Hotel California? WTF? WHY?!