Do you come up with surnames (last names)?

[Voadam]

It varies.

An assortment of past and present PCs

Voadam (Shipmaster Voadam, 1st Merchant's Consul, The Traveller, The Green Wizard)
Jack Morrow
Kalenestarius Floriandin
Garn
Loriallocor
Miltiades Inquisitor of Rao
Gregor Hanville
Aristogoras
Sir Merrick Garland
Hael Boudin
Kevin Carbone
Oban the Tough
Snargle
Snarrek
Thoma Griffith
Cyr Morgant
Kordunn Asteroth

 

[Whizbang Dustyboots]

Yes, yes, I do.

 

[Arkham]

Speaking of D&D only, it depends on the culture of the character.
A character from a small town often has no surname, and only take an appelation when confusion would otherwise result. i.e. Igar Longshanks, for the long-legged Igar, as opposed to Igar Ironsides who generally goes about in a breastplate.
It of course gets more convoluted when a character earns honorifics and titles, or is from or adopted into an important house. i.e. Igar Longshanks, the thrice-blooded, recent of the house of Denovorn, keeper of the Black Blade of the West.

For modern day game, everyone gets all appropriate names.

 

[Boss]

For my last campaign, I didn't make up surnames... usually. It depended upon how the name flowed on its own I guess. But I am currently in the process of designing a new campaign world and I am trying to go the extra length to give surnames in the cultures that have need/use surnames. Not all cultures do in this world, and different cultures use different naming conventions. It is much more difficult and I am in the process of creating charts to use when I need names on the fly for each culture.

 

[Shade]

What he said. For some characters--and some cultures--it's appropriate. Sometimes it's not.

For instance, we're about to start a Mythic Greece campaign. No last names there.

But even in a more traditional setting, it depends on the character, his homeland, and his culture. I've played characters with one name, two names, and occasionally three. I've played characters with titles and honorifics. It all depends, and I don't think I can honestly say I have a standard one way or the other.

Another "what he said" here.

 

[Tonguez]

Tobias Pym
Tomas Alban
Macabre
Ras Benari (Ras = Lord)
Orbril the Gnome Master of the Grand Circus Maximus who is the Day man of a wandering circus has as his formal name Orbril y Magira na Mandina ma Daltine e fanatu which means Orbril (of) clan Magira of Mandina and Daltine (now) wandering) * e fanatu = present continiuous i fanatu would be past perfect

 

[Wombat]

Unless there is some specific reason not to give a surname (the culture my character comes from does not use them, etc.), all my PCs have them.

The same is true for NPCs.

Then again, there are a large number of societies that do not use surnames (most medieval peasants being high on that list). Such individuals always have somesort of distinguishing nickname to tell them apart.

Ask my players about the Seven Arthvins...

 

[Alaric_Prympax]

I usually don't unless the character is a noble or someone of some importence who is distinctive enough to have/need a surname.

 

[Felix]

For mideval fantasy, a surname is a pretension. If the character's lineage matters, then they have a surname.

Everyone else gets by with "Son Of" or thereabouts. Though that's where we get many of today's surnames.

 

[Tonguez]

Everyone else gets by with "Son Of" or thereabouts. Though that's where we get many of today's surnames.

Exactly when the village idiot is named 'Jacob Jacobs son' because he is the son of 'Jacob Miller' its a pretty short step to a legimate surnames