Yaakov meets up with the angel of Esau and battles with him. The angel requests to end the battle so he can depart and Yaakov refuses. In 32:37 we see Yaakov's response, in which he says, "I will not send you, unless you bless me."
Rashi says this is referring to showing that he accepts the fact that Yaakov has the brachos from Yitzhak and will retain no further claims on them.
While I would not dispute that and disagree with Rashi, I would like to offer an alternate pshat, one based on the simple reading of the text.
In the next response of the angel we see that the angel actually blessed Yaakov ("ויברך אותו שם"). That would indicate to me that Yaakov was simply requesting a blessing from this angel.
I would like to point out a thought that came to me when reading this:
We see from here that even people who we might consider evil have the ability to bless, and that, as the gemara says, is something we should take seriously. Do not scoff and reject the blessing of anybody, even if you think they might not be worthy. Yaakov actively sought out the blessing of the angel of Esau who had just tried to kill him and maimed him in the process! Who could represent greater evil than that!!