This one has Spike in a wheelchair on a road trip with Buffy. It is absolutely hilarious! Even the author's notes are entertaining.
A Chance in Hell by dampersandspoons Rated: NC-17 [Reviews - 393]
Summary: Runner-up at the Cradle of Humanity Awards Round 2 for the Be My Mate Award. Runner-up at the Rogue Poet Awards Round 6 for Best Lighthearted. Runner Up at Spark and Burn Round 5 for Best WIP. An apocalypse threat in Maryland requires a vampire's help to disenchant a stone used in the ritual to destroy all of mankind. Since Angelus is still without his soul, Buffy is forced to ask the one vampire she hates for a hand. The problem is, he's in a wheelchair. What happens when a crippled vamp and a slayer make a cross-country trip to save the world? Will they kill each other before they get there, or will her horrible driving do the job for them? But what if they found solace in one another's company instead? Could it be? Yes, it most certainly could.
http://spikeluver.com/SpuffyRealm/viewstory.php?sid=30994&warning=NC-17