So the FanPost topic is present-day trades, but I am not knowledgeable enough about other team's prospects in depth to make any coherent proposals. So instead, I would like to write about some of the best trades the Tigers have ever made.
1. Harvey Kuenn for Rocky Colavito. This was a huge trade, the batting champion for the home run champ and, for several reasons, the Tigers won the trade beyond a shadow of a doubt. At the time, Cleveland's General Manager, Frank Lane, was notorious for constantly making trades. In his career, he made over 400 trades, including Norm Cash, Roger Maris, Rocky Colavito, Enos Slaughter, Red Schoendist and Early Wynn. Lane also traded a manager for a manager (with the Tigers) and tried to trade Stan Musial. Lane will show up twice in this list. Anyway, as to this trade, the 25 year-old Colavito was an extraordinarily popular player who was coming off back-to-back 40 homer seasons. In 4 years with the Tigers, he hit 139 Homers, with slash numbers of .271/.364/.501. He was worth 17.3 WAR in those 4 seasons. Kuenn played one good year with the Indians. He hit .308/.379/.416. Kuenn was worth 2.4 WAR that season. After that season, Lane traded Kuenn to San Francisco for an aging pitcher who went 0-4 for Cleveland and a slightly above replacement-level outfielder.
2. Steve Demeter for Norm Cash. Another Frank Lane special. He had just acquired the 24 year-old Cash from the White Sox, and flipped him to the Tigers for Steve Demeter who went 0-5 for the 1960 Indians and never played in the Majors again (he did play 12 more years in the minors). Cash, on the other hand, is one of the great unsung players of all time, worth 51.7 WAR for the Tigers over the next 15 years. In 1961, Cash rode expansion pitching and corked bats to a .361/.487/.662 season, hitting 41 homers (combined with 45 from Colavito) and leading the Tigers to over 100 wins. Cash was never that good again, but he was consistently solid for the rest of his career, never having an OPS+ below 126 until his final half-season.
3. Andrew Miller, Cameron Maybin and others for Miguel Cabrera [and Dontrelle Willis]. Miller has had a great career as a relief specialist. Maybin's sometimes been an average Centerfielder. Both were first-round picks and highly rated prospects, and both were not good for the Marlins and developed later. Cabrera has been one of the superstars of the Tigers' most-competitive era in team history (at least since 1934-1945), and has been worth 51 WAR for the Tigers over the past 11 years. He will wear the Olde English D on his Hall of Fame plaque. Maybin was worth 3 WAR for the Marlins. Miller was worth a negative 2.4 WAR, and Burke Badenhop was worth almost 2 WAR for them. The other players were worth negative 1.2 WAR for Florida.
4. Ramon Santiago and Juan Gonzalez for Carlos Guillen. Guillen locked down the shortstop position in Detroit from 2004-2008 before bouncing between positions for a couple more years. He was one of the key factors bringing Detroit back to competitiveness, and was worth 18.6 WAR for Detroit, including 6.0 in the great season of 2006. Santiago was worth negative 0.3 WAR for Seattle before being released and returning to Detroit where he backed up Guillen and actually played rather well.
5. Glenn Wilson and John Wockenfuss for Guillermo Hernandez and Dave Bergman. As a young fan in the winter of 1983, I did not understand why the team would trade young and up and coming outfielder Glenn Wilson for journeyman pitcher Willie Hernandez. Turns out the team knew more than I did! Hernandez won the Cy Young and the MVP in 1984, throwing 140.1 innings of incredible relief and teaming with Aurelio Lopez to give the Tigers an incredible bullpen. Hernandez' impact on 1984 can't be entirely measured by WAR, but few relievers ever put up a 4.8 WAR season. He was good for a while after that also (although not quite as good) earning 8.5 WAR for the Tigers. Bergman was a good role player for the Tigers for a long time, and had some legendary at-bats...Wilson had a couple good years for the Phillies, and was worth 6.1 WAR over 4 years. Wockenfuss (a legendary name) had one good year with the Phillies, but that was all. This trade looks more even by WAR than it was on the field.
6. Denny McLain, Don Wert, Elliott Maddox and others for Joe Coleman, Eddie Brinkman and Aurelio Rodriguez. The Tigers got solid value for the remnants of Denny McLain. Only 27 years old, and only 1 year removed from back-to-back Cy Young awards, Denny had worn out both his welcome in Detroit and his right arm. McLain pitched one season for Washington, "earning" a negative 0.4 WAR. Wert, a quality player for Detroit, lasted 20 games for Washington and actually hit for a lower average than McLain (.103 for McLain, .050 for Wert). Maddox had a couple good years for the Washington/Texas franchise. Coleman threw over 280 innings per year for the Tigers between 1971 and 1974 and was a key player on the 72 division championship team. He was worth 15.8 WAR for the Tigers. Brinkman couldn't hit, but was a key fielder for the Tigers. Rodriguez rode his lucky, tattered glove to several good seasons with the Tigers. A below-average hitter, Aurelio was nevertheless worth more than 9 WAR in his years in Detroit and was a lot of fun as a player and an interview subject!
Honorable Mention: Mickey Cochrane for cash + a player [the trade was influenced by Great Depression economics], Aurelio Lopez acquired for Bob Sykes, the Scherzer trade (yes, we gave up good players, but we got more than we gave), Fister acquired for Furbush, Wells and Ruffin.