My personal favorite is probably the standard 2002 GM Goodwrench scheme. Was a terrible year - up until 2009, Kevin's worst by far in terms of results - but the car looked great. It was weird to root for a GM Goodwrench car after all the prior years of rooting against Earnhardt and even in 2001 having quite a few issues with some things Harvick did on the track. The 2003-06 Goodwrench car was pretty awesome looking too. I think I liked the '04 one the best in terms of how the whole car looked with the associate sponsors and everything, but the scheme itself looked great all four years. My favorite special paint scheme from the Goodwrench era was the 2005 reverse scheme, run as a tribute to Earnhardt's Quicksilver car from ten years earlier (part of the GM Goodwrench/RCR 20 year celebration). Unfortunately it got destroyed in the All-Star race after Tony bumped Nemechek and set off a massive pileup that had Kevin and Joe going helmet-to-helmet in the frontstretch grass, haha.
The Shell/Pennzoil scheme looked great on the 2007 Monte Carlo, but didn't lend itself as well to the boxier COT. It still looked decent, but I know a lot of Kevin's fans - in terms of him being their favorite driver I mean - really didn't enjoy his colors being yellow and red, though.
The black Budweiser cars were nice, but I think this year's is the best Bud scheme I've actually watched on TV (first one I remember was Geoff Bodine's solid red car for Junior Johnson in 1990, so I missed the predominantly white cars that Darrell and Terry Labonte - and for 1984, Neil Bonnett - drove, though Kahne did run a throwback complete with period Budweiser decals in 2010 at Darlington I think). I wouldn't mind at all if they peel the 29s off and slap 4s on and keep it as his scheme for next year.
He's had a lot of great Nationwide cars too, the Rheem 33 from 2008-11 and the Reese's 21 from 2004-05 especially jumping out. If Vienna Sausages didn't make me want to throw up I'd probably like the Armour scheme too. The 2003 PayDay car was great too, turned that into my favorite candy bar for nearly the entire season, haha.
As far as cars and trucks he and Delana owned and others drove, have to go with Tony's 33 Old Spice car and the 6 Goodwrench truck that Crafton ('04) and Hornaday ('05) drove.