I don't get it. I kind of want to raise this thinking he's either floating or trying to get a cheap draw. It doesn't really make sense to me that he would be doing this with weaker pairs or sets.
Villain is pretty much unkown 21/4 over 40 hands. No noteworthy hands so far.

$0.25/$0.5 No Limit Holdem
8 players
Converted at weaktight.com

Stacks:
UTG ($43.50)
UTG 1 ($39.74)
Hero (MP1) ($50.21)
MP2 ($121.82)
CO ($109.55)
BTN ($5.00)
SB ($7.00)
BB ($42.45)

Pre-flop: ($0.75, 8 players) Hero is MP1
UTG calls $0.50, UTG 1 calls $0.50, Hero raises to $3, 5 folds, UTG calls $2.50, UTG 1 folds

Flop: ($7.25, 2 players)
UTG checks, Hero bets $5, UTG calls $5

Turn: ($17.25, 2 players)
[color=#cc0000]UTG bets $10



The question is just what kind of range would you give an unkown there?