The federal accessory-after-the-fact statute, 18 U.S.C. 3, can be a tool for creating misdemeanors.  Any federal offense with a two-year maximum can be reduced to a misdemeanor (with a one-year maximum) by pleading to accessory after the fact to that offense.  This is useful where it is important to have a misdemeanor conviction, rather than a felony.  E.g., aggravated felony crimes of violence under 18 U.S.C. § 16(b); TPS felony disqualification.  It is also useful to reduce a two-year maximum to a one-year maximum, to qualify for the Petty Offense Exception to CMT inadmissibility.  See LaFarga v. INS, 170 F.3d 1213 (9th Cir. 1999).  Counsel can do a database search of the entire United States Code and of the Code of Federal Regulations for phrases like "not more than two years" and "not more than 2 years." Two-year offenses are rare, but it would be nice to add them to the stock of offenses which we can use in negotiating misdemeanor pleas.  For valuable lists of federal misdemeanors, see http://ocdw.com/pdf/102907/Federal%20Misdemeanors.pdf;  
http://nycrimbar.org/Members/briefs/Misdemeanors.pdf

Thanks to Joe Beeler.