Be careful of using combat to force pcs together, particually the "getting run out of town sort". Some times a player will unexpectedly turn sourpuss over being put in a no win situation for the purposes of plot.
For example, I needed to add two new pcs to a running 2 month old campaine where one of the plotlines is that an anti arcane, anti "witch" human supremisit religious group has taken over a frontier area. They burned all the "witches" a week ago, and the non humans have left town. The setting is pseudo northern europe. One Player makes a 1/2 ork. Another gives his human rogue an arab name and dress, inculding turban.....The two PCs already in the game are a 1/2 elf wizard, and a dragonborn with a "hat of polymorph to halfling". The set up was, "you meet in a tavern...and the 14 "redneck lumberjacks" throw you out of town together....." The new guys are level 1 one with the established PCs are level 2. The odds are 14 to 4. One player managed to turn what was going to be a worst a "friendly beat down" into a blood bath by pulling an "illegal" weapon after the lumberjacks left thier axes on the pegs "above their table...their table meaning that they didn't even order and the waitress brings them what they always have..." (chairs are "legal" in a "Freindly" racially motivated brawl...rapiers are _not_)
Some players have the misconception that the GM is supposed to always set the players up to win, and take it rather bitterly when they discover that this isn't the case. In this case my attemp to establish a lively and interesting champain world and provide the PCs with rivals or bitter enimies to face later didn't work as the player didn't realize that to have legitimate rivals you have to occationally lose. Of course the other players liked it, and are talking in character about how much they dislike the sect and want to take them down if given the opportunity.
Another tactic that I have had mixed success with in the same game is a "Vision" sequence.
Parapharsing the situtation so my PCs won't know exactly what is going on....You have the party find an sick and incapacitated person (small size race is best) or dog, something that needs a level of healing that the PCs just don't have access to so they only have the option of slowly nursing it back to health. That night the pcs are attacked by something that is overpowering, scary looking, and not quite right , which incapacitates them easily. Then they wake up at mid morning, find that thier patient died during the night, and that they all had the same nightmare about something like giant sized hobgoblins defeating them.
The point of course, is to deliver a message that someone needs a "hero" by showing them the "victim's" perspective of helplessness against the "overwhelming gaint scary monsters". It also give the pcs a reason to have a grudge against say, a party of normal sized hobgoblin slavers that are raiding the local haflings.
In this case, again, some of the players liked it, and though they haven't compleatly figured out what is going on, like that I am giving them reasons to have motivations for getting involved and delivering them in a manner other than "they beg you for help and offer payment". However, the one guy didn't like being in a no win situation, even if it was a dream.